Matanuska-Susitna Wetland Functions and
Values Landscape-Level Assessment
Methodology and Mapping
Prepared by: The Matanuska Susitna Borough
350 E. Dahlia Avenue
Palmer, AK 99645
With support from: U.S. Army Corps of Engineers
Alaska District
CEPOA-EN-CW-PF
U.S. Fish & Wildlife Service
Anchorage Field Office
Habitat Restoration Program
Kenai Watershed Forum
Great Land Trust
May 2014
Mat-Su Wetland Functions and Values
Landscape Level Assessment Methodology and Mapping
1st Edition
Acknowledgements
Numerous individuals, local state and federal agencies, NGOs and private businesses
contributed to the development of this document. A special thank you to the following
individuals who shared their expertise and helped in the review and development of this
document:
Mike Gracz, Kenai Watershed Forum
William Rice, U.S. Fish and Wildlife Service
Matt LaCroix, Environmental Protection Agency
Frankie Barker, Matanuska-Susitna Borough
Michelle Schuman, National Resource Conservation Service
Kim Sollien, Great Land Trust
Maureen deZeeuw, U.S. Fish and Wildlife Service
Nicole Hayes, Corps of Engineers
Emerson Krueger, Matanuska-Susitna Borough
Julie Michaelson, U.S. Fish and Wildlife Service
Dave Mitchell, Great Land Trust
Meg Perdue, U.S. Fish and Wildlife Service
Mary Lee Plumb-Mentjes, Corps of Engineers
Estrella Campellone, Corps of Engineers
John Wros, Great Land Trust
This document should be cited as:
Matanuska-Susitna Borough – Planning Department. 2014. Matanuska-Susitna Wetland
Functions and Values Landscape-Level Assessment Methodology and Mapping. First Edition.
Matanuska-Susitna Borough, Palmer, Alaska. ii+57p.
Disclaimer:
The findings and conclusions in this document are those of the author(s) and do not
necessarily represent the views of the U.S. Fish and Wildlife Service or other agencies.
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Mat-Su Wetland Functions and Values
Landscape Level Assessment Methodology and Mapping
1st Edition
Table of Contents
Introduction……………………………………………………………………………………………………………………………………………….1
Background……………………………………………………………………………………………………………………………………….……….1
Limitations of this Assessment…………………………………………………………………………………………………….…3
Methods…………………………………………………………………………………………………………………….…………………………...….3
Stakeholder Group Involvement……………………………………………………………………………………………………..3
Qualifier Questions…………………….………………………………………………………………………………………...…...…..4
Findings ……………………………………………………………………………………………………………………………………………...……7
Hydrologic Functions
Groundwater Recharge………………………………………………………………………………………………………………….7
Collection, Storage, Discharge………………………………………………………………………………………………………12
Collection……………………………………………………………………………………………………………………….13
Storage…………………………………………………………………………………………………………………………...13
Transmitting Discharge…….…………………………………………………………………………………………….17
Contributing Discharge…………………………………………………………………………………………………...22
Maintenance of Natural Streamflow Regime…………………………………………………………………………………26
Shoreline Stabilization…………………………………………………………………………………………………………………31
Bio-Geochemical Functions
Sediment / Pollutant Storage…………………………………………………………………………………………………….….34
Nutrient Cycling and Storage………………………………………………………………………………………………………..39
Biological Functions
Food Chain Support……………………………………………………………………………………………………………………..43
Anadromous Fish Habitat…………………………………………………………………………………………………………….47
Habitat for Maintenance of Biodiversity……....……………………………..…………………………………………..…...51
Habitat for Species of Concern……………………………………………………………………………………………………..55
Human Identified Values
Recreation…………………………………………………………………………………………………………………………………..61
Consumptive Uses……………………………………………………………………………………………………………………….65
Education……………………………………………………………………………………………………………………………………70
Visual Quality and Aesthetics……………………………………………………………………………………………………….73
Cultural and Historic Importance………………………………………………………………………………………………....76
Uniqueness…………………………………………………………………………………………………………………………………80
References……………………………………………………………………………………………………………………………………………….83
Tables
Table 1. Cook Inlet Classification wetland types within the Mat-Su study area…………………………………………...…7
Table 2. Mapping Results: Groundwater Recharge………………………………………………………………………………….….10
Table 3. Mapping Results: Storage……………………………………………………………………………………………………………..15
Table 4. Mapping Results: Transmitting Discharge….………………………………………………………………………………....20
Table 5. Mapping Results: Contributing Discharge……………………………………………………………………………………..24
Table 6. Mapping Results: Maintenance of Natural Streamflow Regime………………………………………………………29
Table 7. Mapping Results: Shoreline Stabilization………………………………………………………………………………………32
Table 8. Mapping Results: Sediment / Pollutant Storage…………………………………………………………………………….37
Table 9. Mapping Results: Nutrient Cycling and Storage……………………………………………………………………………..41
Table 10. Mapping Results: Food Chain Support……………………………………………………………………………………..….45
Table 11. Mapping Results: Anadromous Fish Habitat………………………………………………………………………………..49
Table 12. Mapping Results: Habitat for Maintenance of Biodiversity……….………………………………………………….53
Table 13. State conservation rank definitions for plants from the Alaska Natural Heritage Program………...….55
Table 14. State-ranked S3 or lower plants intersecting Mat-Su wetlands.…………………..…………………………….…56
Table 15. Species, habitat, and selection criteria for the species of concern…………………………………………………57
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Tables (cont.)
Table 16. Mapping Results: Habitat for Species of Concern……………………………………………………………………..….59
Table 17. Mapping Results: Recreation……………………………………………………………………………………………….……..63
Table 18. Mapping Results: Consumptive Uses…………………………………………………………………….…………………….68
Table 19. Mapping Results: Education…………………………………………………………………………………………………….....71
Table 20. Mapping Results: Visual Quality and Aesthetics…………………………………………………………………………..74
Table 21. Mapping Results: Cultural and Historic Importance……………………………………………………………….……78
Table 22. Mapping Results: Uniqueness…………………………………………………………………………………………………..…81
Maps
Map 1. Cook Inlet Classification wetland types found and current extent of mapping in the MSB...........................5
Map 2. Groundwater Recharge………………………………………………………………………………….................................…...…11
Map 3. Storage……………………………………………………………………………………………………...................................……..…..16
Map 4. Transmitting Discharge….……………………………………………………………………………....................................…......21
Map 5. Contributing Discharge……………………………………………………………………………………........................................25
Map 6. Maintenance of Natural Streamflow Regime…………………………………………………....................................…..…30
Map 7. Shoreline Stabilization…………………………………………………………………………………...................................…..…33
Map 8. Sediment / Pollutant Storage………………………………………………………………………....................................……...38
Map 9. Nutrient Cycling and Storage………………………………………………………………………….....................................…..42
Map 10. Food Chain Support……………………………………………………………………………………........................................….46
Map 11. Anadromous Fish Habitat………………………………………………………………………………........................................50
Map 12. Habitat for Maintenance of Biodiversity…………..………………………………………....................................……..….54
Map 13. Habitat for Species of Concern………………………………………………………………....................................…….....….60
Map 14. Recreation……………………………………………………………………………………………….….......................................…..64
Map 15. Consumptive Uses…………………………………………………………………….……………………........................................69
Map 16. Education……………………………………………………………………………………………………...........................................72
Map 17. Visual Quality and Aesthetics…………………………………………………………………….......................................……..75
Map 18. Cultural and Historic Importance………………………………………………………………......................................…..…79
Map 19. Uniqueness…………………………………………………………………………………………………........................................…82
Figures
Figure a. The Peatland Groundwater System…………………………………………………………………………………………….…9
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Introduction
Mat-Su Wetland Functions and Values
Landscape Level Assessment Methodology and Mapping
1st Edition
In 2007 an interagency wetland advisory group (WAG) was formed to promote wetland
mapping and science within the Matanuska-Susitna Borough (MSB). Concurrently, a wetlands
re-mapping project began in areas expected to receive the greatest permit activity with the U.S.
Army Corps of Engineers (USACE) for wetland dredging and fill activities associated with land
development. With support from the WAG and MSB, the mapping employed a new wetland
classification system, the Cook Inlet Classification (CIC) (www.cookinletwetlands.info) that is
specific to Cook Inlet and locally relevant. In 2010 the WAG, with support from the U.S. Army
Corps of Engineers (USACE), US Fish and Wildlife Service (USFWS) and MSB, embarked upon
an effort to assess the functions and values of all wetlands mapped.
This document reports the results of the assessment and describes the methods used to
develop it. The results are presented in this document as maps and the maps are intended to
guide decision makers in the early stages of project planning, with electronic, high resolution
maps available from MSB. This is a landscape-level, desktop study of wetland functions and
values, the results of which have not been verified in the field. Field work is recommended to
ground-truth the findings if this assessment is to be used in association with regulatory
permitting requirements.
Background
The Mat-Su area is the fastest growing region in the state of Alaska with an average population
increase of 4 percent per year, as compared to 1 percent for the state overall. The population of
the area has more than doubled in the last 20 years and is expected to continue growing. The
population of the Mat-Su’s “Core Area”, including the cities of Palmer and Wasilla, is expected to
double by 2025. Mat-Su growth has been spurred by the desire for affordable housing and
larger lot sizes, which are not readily available in the Anchorage urban area. While most of the
growth and development in the Mat-Su has been on uplands, wetlands are being developed
more often as undeveloped uplands become scarcer.
In 2012, the MSB adopted a comprehensive wetlands management plan intended to increase
awareness of wetlands, define protection measures, and slow the loss of wetlands throughout
the Borough (MSB 2012). The plan focuses on the Core Area, where growth is most likely to
occur. In order to understand how wetlands function across the landscape of the Core Area, the
MSB, together with the USACE and other agencies (WAG), initiated this assessment of wetland
functions and values. This assessment, when used with the MSB Wetlands Management Plan
can help guide development of a more detailed assessment protocol covering individual
wetlands while also addressing cumulative effects by incorporating knowledge of wetland
functions and values across the landscape. This assessment could also inform the future
development of a General Permit under Section 404 of the Clean Water Act.
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Wetland assessments are not new. Many rapid assessment protocols are employed across the
United States to meet the regulatory requirements of section 404 of the Clean Water Act.
However, wetlands in the Cook Inlet Basin present an assessment challenge because the
landscape is markedly different from the landscape of the contiguous U.S. Unlike in the
coterminous 48 states, wetlands in the Mat-Su cover a much greater land surface area
(typically around 40%) and are predominantly peatlands functioning in a reference standard
state, i.e. they are unimpaired. The unique and poorly represented properties of peatlands
combined with the lack of a clear gradient of human disturbance along which to assess wetland
function at a landscape level means that in the Mat-Su a different approach to wetland
assessment is necessary.
Even without a system that addresses the area’s unique character, wetland assessments are
nonetheless required. Wetland assessors have employed a variety of methods in the Mat-Su,
each with positive and negative attributes, to score wetland functions and values. Some
wetland professionals have employed the Alaska District Regulatory Guidance Letter No. 09-01
(RGL) Appendix A: Functional Assessment Information and Tools which involves “Best
Professional Judgment” and a scoring procedure to determine wetland functions and values.
While this is a simple method to use, the methods employed to answer questions are not
always apparent and different wetland values are not always captured. Others have used the
hydrogeomorphic (HGM) approach, which models a scoring metric to assess whether certain
functions and values are performed by individual wetlands. But to measure changes or
differences in the functioning of wetlands it is important to distinguish between two sources of
variation. The first type is natural variation and this type is not measured as functional change
in the HGM approach. The second source of variation is changes due to impacts from human
activity and these are the changes the HGM method is designed to detect. The HGM method
utilizes reference wetlands to measure impacts from human activities to the wetland in
question (Brinson 1996). Since most wetlands in the Mat-Su remain undeveloped and pristine
they would be considered ‘reference standard sites’ thus the HGM approach has extremely
limited applicability currently in the Mat-Su. Additionally, only two wetland types (Flat/Slope
and Riverine) have had HGM models developed in Alaska that might be applicable for use
within the Mat-Su. However, the Riverine model was developed in Southeast Alaska, which has
a very different climate and geography, and the Slope/Flat model was developed for use on the
Kenai Peninsula. Other methods, including a descriptive approach, have also been used. The
lack of a standardized wetland functional assessment methodology for the Mat-Su has resulted
in a patchwork of approaches for different projects, complicating review and making consistent
application of mitigation measures and management practices impossible.
The purpose of this assessment is to assist the MSB in determining wetland functions and
values valid for the region. The methodology developed here is applicable to wetlands mapped
using the Cook Inlet Classification (described below), and can be extended as that ongoing
mapping effort proceeds. The functional analysis in this report is in the development phase and
requires field verification. This is a “living document” that should be modified as information
and science evolves, and as additional Mat-Su wetlands are mapped.
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There has been some debate as to whether to include wetland values in this assessment. Values
are distinct from functions in that values support human health and well-being. Wetland
functions operate independently of human activity. Whereas a wetland will moderate stream
flow regimes independent of human activity, humans may value this stream flow moderation
because of the natural flood control that it produces. Wetlands are often open areas by nature,
and humans often value these openings for view-sheds or winter trail corridors. The
stakeholder group involved in the development of this assessment decided to include values of
wetlands because the assessment will be used by the general public, not just managers and
regulators. There may be additional wetland values (or functions) not considered in the
methodology described here. Wetland assessors should remain open to the possibility that
other values may exist in the area under investigation. The Borough has started the discussion
of values in the Wetland Management Plan, finalized in 2012.
Limitations of this Assessment
The method used to map wetlands for this project is not the only one and other mapping such
as through the National Wetland Inventory still have utility for regulatory purposes. This is a
landscape-level assessment methodology based on nominal scale of 1:18,000 aerial
photography with approximately 15% of wetland polygons ground-truthed. It is useful for
understanding general functions of Mat-Su Core Area wetlands across this unique landscape. A
site-specific methodology could be developed using these methods, but that would require
more extensive testing in the field and more precise delineation of individual wetlands and
project areas. This assessment and mapping effort is a necessary starting point but only by
taking the important next step to develop field based and tested assessment methodologies
specific to the Mat-Su can they best be utilized together in the regulatory process to evaluate
development activities.
Methods
Stakeholder Group Involvement
The following entities were involved in this effort:
•
•
•
•
•
•
•
•
•
•
MSB Planning Department
U.S. Fish & Wildlife Service, Fisheries & Ecological Services
U.S. Army Corps of Engineers, Civil Works Branch – Alaska District
U.S. Army Corps of Engineers, Regulatory Branch – Alaska District
U.S. Environmental Protection Agency
U.S. Department of Agriculture, Natural Resources Conservation Service
Great Land Trust
Kenai Watershed Forum
Solstice Alaska Consulting, Inc.
HDR Alaska, Inc.
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Many other agencies and entities were encouraged to join the stakeholder group, but were
unable to commit to this effort. In addition, stakeholder group members reviewed and
provided comments on this document numerous times throughout the process.
Qualifier Questions
Because this is a landscape-level, desktop study, a methodology had to be developed to
determine the principal functions and values of wetlands using existing data. The study team
decided that the use of GIS would provide the most relevant information for this effort. The
team developed a series of questions for each function and value that could be answered using
existing GIS layers.
The GIS layer central to this effort is the Cook Inlet Classification and map created by Mike
Gracz of the Kenai Watershed Forum (as part of the larger Cook Inlet Basin Wetland
Classification and Mapping program http://cookinletwetlands.info). Between 2007 and 2013,
Gracz used stereoscopic aerial photography, soils and geologic maps, and site visits involving
sediment coring, water chemistry testing, and vegetation sampling to map and describe
wetlands. The GIS mapping is linked to a website providing the information on plant
communities, hydrology, and soils, which was essential to this assessment of wetland functions
and values at a landscape-level.
The portion of the Mat-Su represented for this first edition of the Cook Inlet Lowland Wetlands
Classification and Mapping project encompasses an area of 1,003,233 acres; wetlands comprise
21,290 individual polygons, covering 330,815 acres of the mapped area. Fourteen main
wetland types in the Cook Inlet Classification (CIC) have been identified in the Mat-Su study
area thus far; the large portion of the map shown in the darker grey has not yet been mapped
to classify the wetland types that occur in those areas (Map 1). Detailed information about the
mapping, classification, and field data are available at http://cookinletwetlands.info/.
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Landscape Level Assessment Methodology and Mapping
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Map 1. Cook Inlet Classification wetland types found and current extent of mapping in the
MSB
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Landscape Level Assessment Methodology and Mapping
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Other pertinent GIS source layers used in this assessment included:
•
•
•
•
•
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U.S. Geological Survey (USGS) National Hydrography Dataset (streams, lakes, flowpath,
watersheds)
USGS National Elevation Dataset (topography)
MSB GIS layers (parcels, roads, special use districts, trails, facilities)
Alaska Department of Natural Resources (ADNR) GIS layers (State parks, refuges, game
management areas, trails, recreation sites)
Alaska Department of Fish and Game (ADF&G) GIS layers (anadromous fish habitat,
moose habitat)
Alaska Natural Heritage Program BIOTICS datasets
For each function and value, the study team developed a series of GIS-based questions that
could help exclude or include certain wetland polygons as performing the function or value as a
principal role. In general, questions were related to either the mapping classification, or
spatially explicit information such as the wetlands position in a watershed, proximity to roads
or resources (streams, known fish habitat, etc.). The framework for the assessment, including
the scope of the effort, definition of each function and value, development of questions, and the
mapping results were developed in consultation with the entities listed above. The GIS tools
used to conduct this landscape-level assessment included general overlay functions, selections
by attribute and location, and buffer/proximity tools. These GIS-based questions and tools
were selected to be clear, objective, and repeatable as these were identified as key criteria by
the study team. Recognizing that the understanding of wetland functions and values is not
complete, revisions to assessment methods, questions, or application to expanded new
mapping areas could therefore be made without difficulty.
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Mat-Su Wetland Functions and Values
Landscape Level Assessment Methodology and Mapping
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Findings
Table 1 summarizes the principal wetland functions and values as determined by the
stakeholder group and their acreage within the Mat-Su study area.
Table 1. Summary of wetland functions and values within the Mat-Su study area.
Function or Value
Groundwater Recharge
Storage
Transmitting Discharge
Contributing Discharge
Natural Streamflow Regime
Shoreline Stabilization
Sediment/Pollutant Storage
Nutrient Cycling and Storage
Food Chain Support
Anadromous Fish Habitat
Habitat for Maintenance of Biodiversity
Habitat for Species of Concern
Recreation
Consumptive Uses
Education
Visual Quality/Aesthetics
Cultural and Historical Significance
Uniqueness
Total Area
Principally
Performing this
Function (acres)
146,636
148,652
173,740
147,051
212,589
138,156
253,403
177,086
139,868
202,649
196,264
271,463
251,565
296,654
9,197
155,242
23,375
8,147
Percent of Total
Wetlands Area
44.3%
44.9%
52.5%
44.4%
64.2%
41.7%
76.6%
53.5%
42.2%
61.2%
59.3%
82.0%
76.0%
89.6%
2.7%
46.9%
7.0%
2.4%
The following sections summarize the principal wetland functions and values in the Mat-Su.
Qualifier questions for each function or value are listed and explained, and the detailed results
of the desktop GIS effort to determine which wetlands have which function or value are given.
Maps of the wetland areas with the principal function or value are provided.
HYDROLOGIC FUNCTIONS
Groundwater Recharge
Replenishment of groundwater is an important function in the Mat-Su because groundwater is
the Borough’s primary drinking water source, and because groundwater also supports wetland
hydrologic regimes and the base flows of fish bearing streams. Groundwater, though not as
readily observable as surface water, is closely linked to surface water. Lakes and wetlands in
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Landscape Level Assessment Methodology and Mapping
1st Edition
the Mat-Su Core Area are outcroppings of the groundwater table, which is fed by recharge
largely originating in the Talkeetna Mountains to the north (Jokela et al. 1991). To understand
groundwater, it is useful to divide it into three components: porewater, shallow groundwater,
and deeper groundwater. 1) Porewater is the very shallow groundwater flowing through the
pore spaces in a peatland. Peatlands are wetlands comprised of the partially un-decomposed
remains of plants. Peat deposits are frequently around six feet thick in our area, and the plant
materials at the base of the peat layer frequently date to approximately ten thousand years ago
(Ager and Brubaker 1985; Jones et al. 2009). 2) Shallow groundwater flows through the
unconsolidated glacial deposits that underlie the Core Area. 3) Deeper groundwater flows
through the bedrock beneath the glacial deposits. Groundwater within each of these three
compartments interacts with surface water in a manner that led a group of hydrologists to
entitle their report: “Ground Water and Surface Water, a Single Resource” (Winter et al. 1998).
Wetlands almost always occur in positions on the landscape that directly receive discharge
from shallow groundwater. Therefore, wetlands are not usually important contributors to
groundwater recharge. Conversely, shallow groundwater discharges into the wetland from the
glacial deposits underlying it. Deeper groundwater contributes to the shallow groundwater and
rarely discharges directly to wetlands in the Core Area because wetlands in the Core Area are
almost all underlain by glacial deposits. A few Headwater Fen wetlands mapped on Baldy Ridge
are the exception. Therefore most wetlands act as storage reservoirs of both the shallow
groundwater that flows into them and any precipitation that falls directly on them. There are
three important exceptions.
The first exception is bogs. Bogs are by definition recharge mounds. Bogs form where the
strength of shallow groundwater discharge is weak. Weak discharge is insufficient to transport
exchangeable cations, especially calcium, to the surface. Low calcium concentrations (Boatman
and Lark 1971; Bridgham et al. 1996), along with landscape and climatic factors (Glaser et al.
2004; Rydin and Jeglum 2006), allow the germination of the spores of the Sphagnum mosses
that build bog mounds. The bog mounds are relatively flat and conduct water slowly, especially
in their lower layers, so that these mounds hold precipitation in their pore spaces (Weber
1902; Sjors 1950; Glaser et al. 2004). This porewater recharges underlying substrates (Fig. a).
Depending on the composition and texture of these underlying substrates the porewater may
flow either downward through the deeper peat, when the underlying mineral substrates are
permeable, or horizontally when they are impermeable (Reeve et al. 2001).
Bogs can be distinguished from fens, which are also peatlands, by three criteria: 1) the low
concentration of exchangeable bases, especially calcium (< 2 mg/l); 2) the low pH, produced by
the sphagnum mosses, and 3) by the absence of plants that cannot tolerate these poor
conditions of low pH (very acidic) and low concentrations of exchangeable bases, (Glaser
1992).
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Fig a. The peatland groundwater system. Recharge from uplands, shown by blue arrows, feeds the
shallow groundwater in the glacial sediments (left-hand side and along the bottom of the diagram), and
the lower layers of fen peat. As long as precipitation is sufficient and drainage networks are poorly
developed, bogs form (green mound-shaped unit) where calcium concentrations are low at the surface
of the peat, Concentrations are low because discharge to the fen is dilute, weak, or both. Bogs are fed
almost exclusively by precipitation and support recharge into the underlying fen peat, or deeper
sediments. Bogs may form directly over the glacial sediments if calcium concentration is low.
The second exception to the rule that wetlands do not contribute to groundwater recharge is
those wetlands that occur in the upper reaches of their watersheds. Although these wetlands
often receive groundwater discharge, even in these high positions on the landscape, they also
lose water that may ultimately recharge shallow groundwater lower in the watershed.
The final exception to the rule that wetlands are located in zones of groundwater discharge is
those wetlands that are classified in the Cook Inlet Classification (CIC) as Depressions (Gracz
2013). As mapped in that classification, Depressions can be outcroppings of the water table,
however they are more often areas where snowmelt and rain are stored temporarily before
slowly percolating deeper into the underlying glacial deposits. In the Core Area of the
Matanuska-Susitna Valley, wetlands mapped as Spring Fens are outcroppings of the
groundwater table, and wetlands mapped as Depressions are more likely to store water before
it percolates into shallow groundwater aquifers. Both Spring Fens and Depressions are not
directly connected at the surface to other wetlands or to streams, lakes or saltwater.
Methodology:
Three types of wetlands qualified as contributing to groundwater recharge as a principal
function. These wetlands are: 1) bogs; 2) Depressions; and 3) wetlands lying in the upper 1/3
of their sixth-order Hydrologic Unit Code (HUC) watersheds. The qualifiers are explained
below.
1) Is the wetland polygon classified as a bog (Map Units: ‘LB3’, ‘LB63’, ‘LB36’, ‘DW5’ or ‘DWx5’
or ‘DW5x’ where x is another ‘DW’ hydrologic component) in the CIC?
Notes: Bogs are by definition recharge mounds. They hold a lens of precipitation-derived water
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either directly above an underlying mineral substrate or above underlying fen peat (Fig. a).
That precipitation-derived water is released both as evapotranspiration and diffuse surface
water flow, but it may also recharge the shallow groundwater in underlying substrates (Hill
and Siegel 1991; Siegel and Glaser 1987; Siegel et al. 1995; Reeve et al. 2001). Because the
underlying substrates are receiving groundwater discharging from other sources, the recharge
originating in the bog mound will not often directly recharge deeper groundwater.
2) Is the wetland polygon mapped using the Depression (D) geomorphic component in the CIC?
Notes: Wetlands mapped using the Depression (D) geomorphic component are disconnected at
the surface, and where they do not receive substantial amounts of discharging ground water,
they can recharge underlying aquifers, particularly during periods of drought.
3) Is the wetland located in the upper 1/3 (by area) of its sixth-order HUC watershed?
Notes: Wetlands in the upper portions of their watershed probably recharge shallow
groundwater in the lower portions, at least during periods of drought.
Results:
Based on the qualifier questions, approximately 146,636 acres of wetland in the study area
recharge groundwater as a principal function. The total acres and percent of total wetland area
within the mapped area that answer positive for each qualifier question are found in Table 2.
Table 2. Mapping Results: Groundwater Recharge
Groundwater Recharge Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area Principally
Performing this
Function (acres)
Percent of
Total
Wetland
Area
Is the wetland polygon classified as a bog (Map
Units: ‘LB3’, ‘LB63’, ‘LB36’, ‘DW5’ or ‘DWx5’ or
‘DW5x’ where x is another ‘DW’ hydrologic
component) in the CIC?
42,050
Is the wetland polygon mapped using the
Depression (D) geomorphic component in the CIC?
11,442
Is the wetland located in the upper 1/3 (by area) of
its sixth-order HUC watershed?
108,598
Total
146,636
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
12.7%
3.4%
32.8%
44.3%
wetlands
Map 2 below shows the results for this function; wetland areas shown in the green color have
been determined to contribute to groundwater as a principal function. All maps in this
document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 2. Groundwater Recharge
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Hydrologic Functions of Collection, Storage, and Discharge
The following discussion follows the synthesis of watershed functions by Black (1997) with
recent elaborations by Spence et al. (2011), Spence (2007), and Spence and Woo (2006). These
works assign hydrologic functions, which may vary over time, to elements in a watershed.
Wetlands are important watershed elements and this discussion focuses on them. These
functions are different than the ones often employed in wetland assessment, but they reflect
recent advances in understanding how run-off is generated through the different elements
comprising a watershed in the “element threshold concept” of Spence and Woo (2006).
Regardless of whether or not the threshold concept is the primary mechanism responsible for
streamflow production, it is useful in understanding wetland hydrologic function where
peatlands cover approximately 25% of the landscape.
Black (1997) elucidated three primary functions of any watershed element: 1) Collection, 2)
Storage, and 3) Discharge. A watershed element is an area of a watershed that functions
uniformly within its borders, but differently from adjacent areas. For example a steep bedrock
slope will shed rainfall almost immediately, storing very little of the precipitation, while an
adjacent flat peatland will store most of the same rainfall, releasing it slowly later. The steep
bedrock slope would therefore be a different watershed element than the flat peatland. Spence
and others (2011) divide the discharge function into two functions: contributing and
transmitting.
The collection function depends on characteristics of the storm producing the precipitation,
and on the shape of the watershed and density of the drainage network. Storage occurs
variously within an element, from the pore spaces within peat to the low spots on
microtopography on the surface. Storage depends on slope, the volume and arrangement of
pore spaces, and surface relief. Storage is most active when inflows to a watershed element are
being absorbed before they can flow out.
Discharge is the output from the watershed element and is controlled by the resistance to
leaving storage (Black 1997). Contributing discharge occurs when outflows from the element
primarily originate from storage within the element, i.e. they are greater than inflows to it. A
contributing element will exhibit a constant lowering of its water table produced by outflows
from storage. The volume of outflow from the lowering of the water table will exceed any
inflows. Transmitting discharge occurs when outflow is primarily from the inflows to the
element, i.e. outflow is greater than flow from storage within the element. A transmitting
element will produce outflow without a substantial drop in its water table. The water table is
kept elevated by constant inflow to the element. Inflows can be over the surface, or through
porewater in peatlands, or shallow or deeper groundwater in mineral substrates. An element
(e.g. a wetland) may switch between storing, contributing and transmitting, depending upon
antecedent conditions. These functions are described in more detail below.
A slight shift in emphasis from the watershed element approach described above is needed for
application to our landscape, which is different than the landscape of the Canadian Shield
where much of the work developing this concept has been performed. In that landscape, where
bare bedrock is abundant and wetlands are small watershed elements, surface runoff is
important. On our landscape, where porous glacial till and extensive peat deposits are large
watershed elements, shallow groundwater flow, and flow through pore spaces in peatlands are
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more important. The importance of subsurface inflows and outflows on our landscape requires
a shift in emphasis from runoff to groundwater and porewater movement. For example, instead
of discharging run-off directly to a down-gradient watershed element, a typical wetland
element in our watersheds may primarily discharge diffuse outflows of porewater to
down-gradient elements.
In other areas, where surface flows are more important, factors such as the constriction of
inlets and outlets, or surface roughness are used to assess storage and discharge functions. The
nature of outlet constriction and surface roughness is more important for small wetlands
situated in floodplains, and those with a single outlet stream regulated by a sill, such as a
beaver dam or where a wetland is situated in the headwaters of a first-order stream. These
wetlands certainly occur in the Matanuska-Susitna Valley, but they are not nearly as extensive
as the peatlands that cover much of the wetland landscape here. Because most flow in
Matanuska-Susitna Valley wetlands is through porewaters, the factors influencing the hydraulic
conductivity of the peat (the velocity at which porewater can flow through the peat) and the
volume of pore space available for storage are more important for assessing storage and
discharge functions.
Collection
The first function, collection, depends on characteristics of the precipitation-producing event
and the shape and drainage density of the watershed. The collection function is important to
understand, but it has limited applicability to wetland assessment. In the MSB the most
important characteristic of the collection function is that watershed elements receiving more
precipitation, such as ones at the higher elevations of the Talkeetna Mountains, will collect
more than elements receiving less precipitation, such as lower Wasilla Creek. Therefore the
location of a wetland within its watershed with regards to the distribution of precipitation in
the watershed is the most important factor distinguishing which wetlands perform the
collection function more than others. Since collection is primarily related to watershed
position, shape, and storm event characteristics, little practical application to wetland
assessment and mitigation is possible, therefore, it will not be included as a component of this
assessment. Rain falls on a parking lot the same as it falls on a wetland. However, the fate of the
collected precipitation can be strongly altered by wetland fill and be mitigated for. Therefore,
because the storage function and the two types of discharge function, transmission and
contribution can be altered, they will be assessed here.
Storage
Storage is the intermediary between the collection of water in a watershed element and its
discharge (Black 1997). Storage occurs in at least six important compartments: 1) depressions,
2) channels, 3) detention (water held in the saturated zone and released within 24 hours); 4)
retention (water held in the unsaturated zone by capillary forces); 5) groundwater (water held
for more than 24 hours); and 6) vegetation. The ability of a wetland to store water depends on
antecedent conditions as well as the hydraulic gradient (the elevation difference of water levels
within an element or between elements), the character of the vegetation, the surface
micro-relief, and the volume, distribution, and shape of available pore spaces.
Storage capacity is an important control on the natural stream flow regime of a watershed.
Watersheds with greater storage capacity support streams with more stable discharges than
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watersheds with lower storage capacity, especially in response to storm events and prolonged
dry periods. Natural stream flow regimes are what determine the form and physical habitat
characteristics of a stream. Higher flows can produce streams with larger bed materials, or
more riffles, for example. Changes in flow regime will therefore ultimately influence in-stream
habitat conditions. Therefore changes in the storage capacity of a watershed element will
ultimately affect the habitat and flooding characteristics of streams in the watershed.
Wetlands that store water as a principal function are flat wetlands with well-developed
micro-relief and more frequently contain large volumes of empty pore spaces. Additionally,
wetlands disconnected from the drainage network will primarily store inputs. Most peatlands
satisfy the criterion of being flat, and peatlands exhibiting greater variability in water level
through the growing season more often have larger volumes of empty pore space available for
storage. These peatlands also typically exhibit greater micro-topographic relief.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
storage as a principal function within the Mat-Su.
1) Is the wetland polygon mapped using a hydrologic code greater than or equal to 3 in the CIC?
Notes: Wetlands with a hydrologic code greater than or equal to 3 are peatlands supporting
water levels that are variable through the growing season (Gracz 2013). This is an indication
that precipitation inputs can be more often stored in a larger volume of available pore space.
2) Is the wetland polygon mapped using the Depression (D) or Spring Fen (SF) geomorphic
component in the CIC?
Notes: Depressions and Spring Fens are disconnected at the surface from other wetlands and
water bodies. Because they are disconnected, the flows out of them are slower, through shallow
groundwater pathways. Therefore precipitation on the wetland is more often stored than
discharged directly to other water bodies.
3) Is the wetland polygon mapped using the map units ‘LBSF’ or ‘DWR’ in the CIC?
Notes: Wetlands that are classified as ‘LBSF’ and ‘DWR’ are large heterogeneous peatland
complexes supporting well-developed micro-topography. Wetlands with well-developed
micro-topography are expected to support a greater storage capacity than more homogeneous
wetlands.
4) Is the wetland mapped as a Wetland/Upland complex (‘WU’) in the CIC? Notes:
Wetland/Upland complexes are where wetlands cover at least 30% of an area and are mixed
with uplands at a scale too fine to delineate separately at 1:18,000. This can be because small
depressions dot an area of upland or because the water table varies subtly around a foot below
the surface over flatter landscape. Areas with the water table within a foot of the surface for a
few weeks of the growing season are wetlands. In the case of the small depressions, the
well-developed hummocky topography creates ample space for storage of groundwater, both
in pore spaces of the uplands and on the surface of the depressions. In the case of the flatter
landscape, the often deeper water tables will support a large volume of available pore space
over a low gradient, conditions ideal for storage.
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Results:
Based on the qualifier questions, approximately 148,652 acres of wetland in the study area
provide hydrologic storage as a principal function. The total acres and percent of total wetland
area within the mapped area that meet the criteria for each qualifier question are found in
Table 3.
Table 3. Mapping Results: Storage
Storage Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function (acres)
Percent of Total
Wetland Area
Is the wetland polygon mapped using a hydrologic
code greater than or equal to 3 in the CIC?
139,565
Is the wetland polygon mapped using the Depression
(D) or Spring Fen (SF) geomorphic component in the
CIC?
14,087
Is the wetland polygon mapped using the map units
‘LBSF’ or ‘DWR’ in the CIC?
22,709
Is the wetland mapped as a Wetland/Upland
complex (‘WU’) in the CIC?
2,879
Total
148,652
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
42.1%
4.2%
6.8%
0.8%
44.9%
wetlands
Map 3 below shows the results for this function; wetland areas shown in the green color have
been determined to perform storage as a principal function. All maps in this document are
available for download in a high resolution version at: http://cookinletwetlands.info/
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Map 3. Storage
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Transmitting Discharge
Discharge from wetlands can be divided into two types: contributing and transmitting. A
wetland is transmitting discharge when inflows to the wetland are greater than flows from
storage in the wetland. Therefore, in a transmitting wetland most of the discharge from the
wetland polygon is from inflows to it that are passing through, not from storage within it, and
thus outflow is produced without a lowering of the water table. In contrast, a wetland is
contributing discharge when flows from storage within the wetland exceed inflow to it (Spence
et al. 2011).
Here we emphasize diffuse porewater exchanges shared among elements, rather than surface
run-off, because porewater and shallow groundwater inputs and outputs dominate flows into
and out of our peatlands. Most inflows to and outflows from the peatland are through shallow
groundwater and porewaters, because the infiltration capacity of unsaturated peat is high and
gradients are shallow so that surface drainage networks are poorly developed. Even when the
peatland is saturated to the surface, the elasticity of the peat aquifer allows further storage, and
the peatland may still primarily discharge porewater.
Wetland polygons (elements) supporting stable water levels near the surface are likely
receiving constant inflow from up-gradient. The steady up-gradient supply will probably
exceed the amount of discharge generated from storage within the wetland. The wetland will
produce discharge from porewater without a substantial decline in its water table. When an
element is discharging and inflow exceeds discharge from storage the watershed element is
transmitting discharge (Spence et al. 2011).
Wetland polygons that are transmitting discharge as a principal function act as filters and
detain storm water flows. They are an important component of a stream’s natural flow regime.
If the rate of transmission is altered, the form of the down-gradient stream will change, and
filtration could become ineffective. A changed stream form will support different habitat
conditions and a loss of filtration will negatively impact water quality. Since wetlands are
usually replaced with relatively impervious surfaces, the change will be more frequent floods
with higher peak discharges, and lower dry-season flows of more polluted water.
Methodology:
Below is a list of qualifiers that were used to select wetlands considered to be transmitting
discharge as a principal function.
1) Is the wetland polygon mapped using the Depression (D) geomorphic component in the CIC?
Notes: Because depressions are disconnected from the stream network except through ground
water, and have weak groundwater connections, these wetlands ARE NOT transmitting as a
principal function. They are excluded from wetlands meeting the following criterion
(hydrologic component <3)
2) Is the wetland polygon mapped using a hydrologic component less than 3 in the CIC (but not
mapped with the geomorphic component Depression, or covered below)?
Notes: Wetland polygons with a hydrologic component less than 3 have a water table that is at
or near the surface for most of the growing season (Gracz 2013). This is a likely an indication of
a continuous supply of groundwater and porewater to the polygon. Because inflow is
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maintaining a water level near the surface, inflows probably exceed discharge from storage,
meeting the definition of a transmitting watershed element (Spence et al. 2011). Depressions
are excluded because they are not connected to the stream network, and generally have weak
groundwater connections. Spring Fens are also disconnected from the stream network,
however Spring Fens have strong groundwater connections. These strong connections
frequently maintain water levels near the surface. Falling water levels would indicate that
discharge is primarily originating from storage within the polygon (or lost to evaporation), but
since the water level is stable near the surface, most discharge is likely maintained by inflows,
see below.
3) Is the wetland polygon mapped using the Discharge Slope (S), Abandoned Meander Terrace
(AMT), Drainageway (DW), Riverine (R), Very Large Dune (VLD) Trough (RT), or Spring Fen
(SF) geomorphic component of the CIC?
Notes: Discharge Slopes (S) are mineral soil wetlands located at slope breaks. They are found at
foot- and toe-slope positions, often adjacent to peatlands where a steady supply of shallow
groundwater frequently maintains stable water levels near the surface (Gracz 2013). Because
inflow is maintaining a water level near the surface, inflows probably exceed discharge from
storage, meeting the definition of a transmitting watershed element (Spence et al. 2011).
Abandoned Meander Terraces (AMT) are peatlands on terraces adjacent to rivers that are no
longer part of the modern flood plain. AMTs may receive inflows originating over large areas of
the watershed, thus frequently have stable water levels near the surface. Because inflow is
maintaining a water level near the surface, inflows probably exceed discharge from storage,
meeting the definition of a transmitting watershed element (Spence et al. 2011).
Drainageways (D) are peatlands in relict valleys that once drained more extensive glaciers.
DWs occur in landscape positions that receive a steady supply of shallow groundwater (Gracz
2013). The steady inflow usually maintains a stable water level near the surface. Because
inflow is maintaining a water level near the surface, inflows probably exceed discharge from
storage, meeting the definition of a transmitting watershed element (Spence et al. 2011).
Riverine (R) wetlands are streams and their associated valley bottoms. In perennial streams,
storage is generally transient through a porous substrate, so that internal storage from the
polygon usually cannot contribute more to outflow than upstream inflow, especially in gaining
reaches. In losing stream reaches, flows from transient storage within the hyporrheic zone of
the reach will contribute to outflow somewhere downstream but probably these flows from
storage do not often exceed inflows from upstream. Therefore polygons (elements) mapped
using the ‘R’ geomorphic component will most often be transmitting discharge.
Very Large Dune (VLD) Trough (RT) wetlands are peatlands in the troughs between very large
dune features. Found in the Meadow Lakes area the very large dunes may have been formed
during a mega-glacial outburst flood originating at glacial Lake Atna sometime near the end of
the last glacial maximum (Wiedmer et al. 2010). VLD Trough wetlands often support a
bisecting stream. Because the adjacent unconsolidated sediments are often coarse-grained
cobbles and gravels, which conduct groundwater flow easily, t receive a steady supply of
shallow groundwater. The steady inflow usually maintains a stable water level near the surface.
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Because inflow is maintaining a water level near the surface, inflows probably exceed discharge
from storage, meeting the definition of a transmitting watershed element (Spence et al. 2011).
Spring Fens (SF) are small peatlands found between Houston and Palmer that lie in
closed-basin depressions with strong connections to ground water. They occur where surface
topography intersects the relatively shallow water table and are frequently underlain by thick,
well-sorted and coarse-grained glaciofluvial sediments allowing high rates of groundwater flow
(Jokela et al. 1991; Kikuchi 2013). Water levels in these wetlands are connected to other
wetlands and to streams only through shallow unconfined groundwater movement through
these porous sediments. Because these sediments can provide a steady supply of shallow
groundwater, water levels in Spring Fens vary the least of any geomorphic type (Gracz 2013).
The steady inflow usually maintains a stable water level near the surface. Because inflow is
maintaining a water level near the surface, inflows probably exceed discharge from storage,
meeting the definition of a transmitting watershed element (Spence et al. 2011).
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Results:
Based on the qualifier questions, approximately 173,740 acres of wetland in the study area
transmit discharge as a principal function. The total acres and percent of total wetland area
within the mapped area that meet the criteria for each qualifier question are found in Table 4.
Table 4. Mapping Results: Transmitting Discharge
Transmitting Discharge Criteria
Total Area Meeting
Question Criteria
(acres)
Total Area
Principally
Performing this
Function (acres)
Percent of Total
Wetland Area
Is the wetland polygon mapped using a hydrologic
component less than 3 of the CIC (but not mapped
with the geomorphic component Depression (D), or
those covered below)?
50,853
Is the wetland polygon mapped using the Discharge
Slope (S), Abandoned Meander Terrace (AMT),
Drainageway (DW), Riverine (R), VLD Trough (RT),
or Spring Fen (SF) geomorphic component of the
CIC?
124,693
Total
173,740
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
15.3%
37.6%
52.5%
wetlands
Map 4 below shows the results for this function; wetland areas shown in the green color have
been determined to contribute to discharge by transmission as a principal function. All maps in
this document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 4. Transmitting Discharge
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Contributing Discharge
Discharge is outflow from a watershed element (Black 1997; Spence et al. 2011). Discharge
from wetlands can be divided into two types: contributing and transmitting. A wetland is
transmitting when inflows to the wetland are greater than any flow generated internally from
storage in the wetland. These wetlands produce outflow without a substantial lowering of the
water table. In contrast, a wetland is contributing when flow from storage within the wetland
most often exceeds the inflows to it (Spence et al. 2011). In contributing wetlands, outflow
causes a substantial lowering of the water table.
Those wetlands with variable water levels likely receive a more substantial portion of their
input from snowmelt and storm events, rather than from a steady inflow of groundwater and
porewater from up-gradient especially if the wetland straddles a watershed divide. In fact,
these wetlands may support a high variation in their water levels because no other watershed
elements are positioned up-gradient. When no other elements lay up-gradient no inflow to the
element is possible, and since transmitting discharge requires that inflows exceed outflow, the
element cannot be transmitting (Spence and Woo 2006). Rather, the element is contributing
flow. Contributions originate from water held in storage, which is replenished primarily by
snowmelt or rain events and less by constant groundwater or surface inflow. Inputs from
snowmelt and rain events are relatively brief compared to the constant input from
groundwater. Bogs are almost always contributing elements because in bogs inflows from
groundwater are largely absent, precipitation is almost always the only input, and therefore
outflows are almost exclusively from storage following rain events and snowmelt (Siegel et al.
1995) (see also Fig. a).
Wetlands that are most often contributing are important in maintaining stream flow during dry
periods, and in attenuating storm flows. The ability of a wetland polygon to contribute overlaps
with its ability to store water, as internal storage is a pre-requisite for contribution. If the
storage capacity of the wetland is reduced due to excavation of the peat, for example, then less
stored water will be available for stream flow during dry periods, which will also have an effect
on stream temperature, because a smaller mass of water will heat more quickly. Further, a
smaller storage capacity will be available to absorb water from storms, resulting in higher
flows more frequently. More frequent higher flows will transport larger particles, which alters
streambed characteristics. In combination with lower dry-season flows the altered bed can
have negative effects on spawning habitat, for example.
Methodology:
Below is a description of the rationale for selecting or excluding wetland polygons that were
considered to be contributing discharge as a principal function.
1) Is the wetland polygon mapped using the Depression (D) geomorphic component of the CIC?
Notes: Depressions are disconnected from the stream network. Inflows are frequently from
weak local groundwater sources and precipitation events. Depressions as a whole frequently
exhibit seasonally variable water levels, even as some areas within the Depression are
permanently flooded. The variation in water level indicates discharge from internal storage is
greater than inflows (through shallow groundwater pathways). Watershed elements with
greater discharge from storage than from inflow are contributing (Spence et al. 2011).
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2) Is the wetland polygon mapped using a hydrologic component greater than or equal to 3 in
the CIC (but not mapped with the geomorphic component Depression, which is covered
above)?
Notes: Wetlands mapped with a hydrologic component greater than or equal to 3 support
water levels that are seasonally variable, indicating that they likely do not receive a steady
supply of groundwater or porewater from up-gradient watershed elements. Snowmelt and
precipitation events drive higher water levels, which fall during dry periods. Therefore, outflow
generated from storage in these wetland polygons probably most often exceeds inflows,
meeting the definition of a contributing watershed element (Spence et al. 2011).
3) Is the wetland polygon mapped using the map units ‘LB3’, ‘LB36’, ‘LB63’, or include the
‘DW5’ hydrologic component (NOTE that 5A is not the same as 5; e.g. ‘DW5A’ or ‘DW5A3’ do
not include the DW% component) in the CIC?
Notes: Wetlands mapped as ‘LB’3, ‘LB36’, ‘LB63’, ‘DW5’ are bogs (‘DW5A’ is a forested, non-bog
component). Precipitation is the dominant water source to bogs, which receive little or no
inflow from groundwater (Fig. a). Therefore, most discharge from bogs is from internal storage.
Watershed elements discharging more from storage than from inflows are contributing
elements (Spence et al. 2011).
4) Is the wetland mapped as a Wetland/Upland complex (‘WU’) in the CIC? Notes:
Wetland/Upland complexes are where wetlands covering at least 30% of an area occur mixed
with uplands at a scale too fine to delineate separately at a scale of 1:18,000. This can be
because small depressions dot an area of upland or because a deeper water table varies subtly
over flatter landscape. In the case of the small depressions, the well-developed hummocky
topography creates ample space for storage, both in pore spaces of the uplands and on the
surface of the depressions. In the case of the flatter landscape, the often deeper water tables
found over WUs on flatter landforms will support a large volume of available pore space over a
low gradient, conditions ideal for storage. In both types the internally stored water is slowly
released during dry periods. The variation in water levels indicates that inflows are smaller
and/or more sporadic and outflow is frequently generated from storage, meeting the definition
of a contributing watershed element (Spence et al. 2011).
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Results:
Based on the criteria above, approximately 147,051 acres of wetland in the study area
contribute discharge as a principal function. The total acres and percent of total wetland area
within the mapped area that meet the criteria for each qualifier question are found in Table 5.
Table 5. Mapping Results: Contributing Discharge
Contributing Discharge Criteria
Total Area Meeting
Question Criteria
(acres)
Total Area
Principally
Performing this
Function (acres)
Percent of Total
Wetland Area
Is the wetland polygon mapped using the Depression
(D) geomorphic component of the CIC?
11,442
Is the wetland polygon mapped using a hydrologic
component greater than or equal to 3 in the CIC?
139,565
Is the wetland polygon mapped as ‘LB3’, ‘LB36’,
‘LB63’, or with the ‘DW5’, (NOT 5A) map unit in the
CIC?
38,601
Is the wetland mapped as a Wetland/Upland
complex (‘WU’) in the CIC?
2,879
Total
147,051
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
3.4%
42.1%
11.6%
0.8%
44.4%
wetlands
Map 5 below shows the results for this function; wetland areas shown in the green color have
been determined to contribute to discharge by contribution as a principal function. All maps in
this document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 5. Contributing Discharge
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Maintenance of Natural Stream Flow Regime
Stream flow is a physical process determined by the slope of the stream, its sediment supply,
the land cover of its watershed, and the climate. Surprisingly, the character of a stream- the
length and radius of its meanders and the nature and distribution of its bed materials- is largely
controlled by smaller, more frequent floods and not by catastrophic events (Wolman and Miller
1960). These smaller frequent flood events are the ones that barely overtop stream banks and
are termed bank-full events, they occur once every one or two years on average (Wolman and
Miller 1960; Rosgen and Silvey 1996; Brooks et al 2003). In fact, it is these common floods that
shape the nature of the stream banks themselves. Since bank-full events transport most of the
sediment over time, any changes in the magnitude or frequency of these events will change the
character of the stream.
It is important to note that wetlands and other storage reservoirs in a watershed have little
control over the effects of large catastrophic floods. Wetlands and other storage reservoirs can
slow the consequences of catastrophic events to a point, but more important is their control
over the bank-full events that actually do most of the work. If the frequency and magnitude of
the bank-full events changes, then the distribution of bed materials and the character of the
floodplain will change because it is the work that bank-full floods perform that exerts the
primary control over the shape of the stream and its floodplain.
Changes in the land cover in a watershed can have profound effects on the magnitude and
frequency of bank-full events. If wetlands are replaced with fill pads, for example, bank-full
events will increase in frequency and magnitude. A bank-full event that was once a one-to-two
year flood may now recur more often, and the new one-to-two year flood will be larger, so that
perhaps what used to be a flood that occurred every ten years now occurs every two years
(Bledsoe and Watson 2001). If the new bank-full flood is now what used to be a ten-year flood,
then the banks and bed of the stream will adjust. This adjustment will have major
consequences for people living along the stream, and for the habitat within the stream. People
living outside of the former floodplain may now find themselves within the new floodplain,
erosion will increase, and spawning gravels will be displaced. Maintenance of the natural flow
regime of the stream is thus highly desirable, and changes to the flow regime will produce
changes that may be unacceptable, or require expensive measures to fix.
A wetland delays the release of water during and following precipitation events by storing and
detaining water within its pore spaces and over its flat surface. This delayed release reduces
the magnitude of the peak flow associated with the storm and maintains the natural flow
regime of down-gradient streams. Without this detention and storage, the event water would
flow down-gradient at a faster rate, resulting in higher water levels in the stream more quickly
than with the detention and storage.
Further, the slow release of water from wetlands may also sustain stream flows during dry
periods and provide a continuous source of outflow to watershed elements laying
down-gradient (Dunne and Leopold 1978; Brooks et al. 2003; Spence and Woo 2006; Spence et
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al 2011). It is possible for an individual wetland to be singularly effective in maintaining stream
flow. However, moderation of stream flow is more often the result of the interrelated
functioning of a network of watershed elements (Black 1997; Spence and Woo 2006). The
maintenance of streamflow during dry periods may partially mitigate the effect that climate
change will have on expected increases in stream temperatures because more water in the
stream during a dry period will require more heat to raise its temperature the same amount.
The capacity of a wetland to temporarily store and detain water on the surface and in shallow
ground water depends on antecedent conditions, restrictive soil layers, the volume and
distribution of available pore spaces, and micro-and macro-topographic relief. Organic soils
support a greater storage capacity than mineral soils due to their exceptionally high volume of
unconnected pore spaces. For example, peatlands are composed of 90-97% water when
saturated (Clymo 1983). Even when local peatlands are saturated to the surface considerable
storage capacity may still be available due to the elasticity of the peat aquifer.
Flat wetlands with water levels that are variable through the season and that are not directly
connected at the surface to the stream network most strongly maintain and buffer natural
stream flow regimes. These wetlands have more surface relief, more often support the
antecedent conditions that allow for more storage, and most effectively slow down-gradient
outflow, and once storm input ceases, release flow from storage for longer periods.
Methodology:
Below is a list of qualifiers that were used to select wetlands considered to maintain natural
stream flow regimes as a principal function.
1) Is the wetland polygon mapped using the Riverine (R) geomorphologic component of the
CIC?
Notes: ‘R’ polygons are Riverine wetlands including rivers and streams and their associated
valley bottoms. These wetlands define the shape of the stream, therefore any alterations to
these wetlands will directly influence the natural flow regime. The margins of these wetland
polygons provide an important buffer for run-off to the stream. If run-off from impervious
surfaces is directly connected to the stream (termed, effective impervious surface) and no
buffer is present to detain that run-off, stream water quality will become degraded with a
lower cover of impervious surface than in a watershed where the impervious surface is not
directly connected to the receiving water (Bledsoe and Watson 2001).
2) Is the wetland complex large compared to its watershed?
Notes: For this landscape-scale functional assessment, large is defined in relation to a
sixth-order Hydrologic Unit Code (HUC) watershed as mapped by the U.S. Geologic Survey. In
watersheds the size of sixth-order HUCs, individual wetland polygons comprising 3% or more
of the watershed’s total area were considered large. This is based on methods for assessing
flow retention and flood control found in the Anchorage Wetland Assessment Method
(Appendix B, pg. 159) of the Anchorage Wetlands Management Plan (Municipality of
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Anchorage, 1996), in which a point system is used to assign a score based on wetland area as a
proportion of watershed area. The maximum score is 25 points, from this maximum score a 15
point threshold (60% of maximum) was used to define large wetlands which correlates to the
3% of total area value for individual wetland polygons. Thus large wetlands have an
approximate size range of 300 – 1200 acres, based on the typical size range of 10,000 – 40,000
acres for USGS mapped sixth-order HUCs (NRCS 2010). In the Mat-Su Cook Inlet Classification
(CIC) mapping, contiguous large riverine wetland polygons may sometimes extend outside
sixth order HUC boundaries. In these cases, the polygon was evaluated by only considering the
portion of the riverine wetland polygon within each HUC. Each of these percentages were
calculated and if any one portion of the polygon had a value of 3% or greater in relation to that
HUC then the entire polygon was attributed as ‘large’. Large wetlands have more area and pore
volume for storage than smaller wetlands thus contributing more to flow retention and flood
control.
3) Is the wetland located in the upper 1/3 (by area) of its sixth-order HUC watershed?
Notes: Wetlands in the upper portions of their watershed may potentially regulate flow to a
larger down-gradient area than wetlands in the lower portions of their watershed.
4) Is the wetland polygon hydrologic code greater than or equal to 3 and adjacent to a wetland
mapped with the Riverine (R) geomorphic component of the CIC?
Notes: Wetland polygons mapped using a hydrologic component greater than or equal to 3 are
those with seasonally variable water levels. Wetlands with seasonally variable water levels
more often support a larger volume of available pore space to absorb precipitation and slowly
release it later. Wetland polygons mapped adjacent to Riverine wetlands are in a position to
immediately buffer the natural stream flow regime, and alterations to these wetlands are more
likely to have disproportionately larger effects on the natural flow regime (Bledsoe and Watson
2001).
5) Is the wetland mapped using the Depression (D) or Spring Fen (SF) geomorphic component
of the CIC?
Notes: Polygons mapped using the Depression (D) geomorphic component are surrounded by
uplands, so that there is no surface or wetland connection to a navigable water body. Without a
surface connection, they are particularly effective at diverting storm water flow into long-term
storage as groundwater. In the watersheds where Depressions are numerous, they may be the
only natural features that substantially detain and store storm flow.
Wetlands mapped using the Spring Fen (SF) geomorphic component are small peatlands
surrounded by uplands where surface topography intersects the relatively shallow water table
(Jokela et al. 1991). Like Depressions, they lack a surface connection to the stream network and
therefore are particularly effective at diverting storm flow to long-term storage as
groundwater, thus buffering peaks of the natural flow regime. Because Spring Fens are located
in an area where evaporation and transpiration by plants exceeds precipitation, they may be
the only wetlands available for storage and diversion of precipitation produced during storm
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events. If these wetlands become connected to the surface water network through drainage,
then the natural flow regime of receiving waters will be altered.
Both Depressions and Spring Fens are often located in watersheds with low wetland cover,
therefore their small size may represent a significant portion of the wetland cover within the
surrounding sixth-order HUC watershed.
Results:
Based on the qualifier questions, approximately 212,589 acres of wetland in the study area
maintain natural streamflow as a principal function. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 6.
Table 6. Mapping Results: Maintenance of Natural Streamflow Regime
Maintenance of Natural Stream Flow Regime Criteria
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function (acres)
Percent of Total
Wetland Area
Is the wetland polygon mapped using the Riverine
(R) geomorphologic component of the CIC?
88,923
Is the wetland complex large compared to its
10,899
watershed?
Is the wetland located in the upper 1/3 (by area) of
its sixth-order HUC watershed?
108,598
Is the wetland polygon hydrologic code greater than
or equal to 3 and adjacent to a wetland mapped with
the Riverine (R) geomorphic component of the CIC?
64,673
Is the wetland mapped using the Depression (D) or
Spring Fen (SF) geomorphic component of the CIC?
14,087
Total
212,589
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
26.8%
3.2%
32.8%
19.5%
4.2%
64.2%
wetlands
Map 6 below shows the results for this function; wetland areas shown in the green color have
been determined to maintain the natural stream flow regime as a principal function. All maps
in this document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 6. Maintenance of Natural Streamflow Regime
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Shoreline Stabilization
Wetland vegetation can often stabilize stream banks and pond or lake fringes, as these areas
are prone to erosion. Along some stream banks or lakeshores, erosion and bank collapse can
reduce the availability of cover, degrade water quality, and reduce the suitability of coarse
sediment important for salmon spawning, at least temporarily (Adamus Resource Assessment
1987). There are two types of stabilization that wetlands provide in these environments,
shoreline anchoring and dissipation of erosional forces. Vegetation can bind and stabilize
substrates, with studies showing significant decrease in erosion with vegetated vs. unvegetated
shorelines. Shoreline vegetation also dissipates erosive forces of currents and waves, with their
effectiveness dependent on the magnitude of the erosive force and type of vegetation present
(Adamus, et al., 1991). Other studies have also shown that the width of the vegetated bank,
efficiency of the vegetation in trapping sediments, soil composition of the bank or shore, height
and slope of the bank or shore, and the elevation of the toe of the bank relative to mean high
water are also significant (Sather and Smith 1984).
Where inundation events are common, wetlands that are adjacent to surface waters for a
longer duration generally provide this function more frequently than do wetlands that are
adjacent to surface waters for a shorter duration. Where plant cover exists along shorelines,
the principal factors determining the degree of shoreline protection are the ability of the plants
to survive prolonged flooding and their resistance to undermining (NWTC 1978). There may be
other overriding factors affecting bank stability, such as soil texture (sand and gravel are highly
erodible whereas soil with cohesive aggregates is not) and soil layering (e.g., a layer of cobbles
or gravel will be stable in low velocity water but less so in higher velocity water). Vegetation
with deep, soil-binding root masses like bluejoint reedgrass, trees, or shrubs, are more effective
at stabilization than species with less dense root systems. Primary function will be given to
wetlands that have adjacency to a stream, lake or pond.
Methodology:
Below is a list of criteria that were used to select wetlands that stabilize sediments and
shorelines as a principal function within the Mat-Su.
1) Is the wetland polygon mapped using the Riverine (R) geomorphic component of the CIC or
immediately adjacent to a stream, lake, or pond (adjacent to a polygon mapped using the
‘LAKE’ map unit, a riverine polygon, or a polygon mapped using a hydrologic component =1)?
Notes: Wetlands with surface water or wetlands immediately adjacent to water bodies, flowing
or not, have the opportunity to perform shoreline functions. Polygons with a hydrologic
component of ‘1’, or classified with the geomorphic component ‘R’, or ‘LAKE’ or polygons
intersected by a stream were selected. A hydrologic component equal to 1 indicates a wetland
that has ponded surface water all year over at least 10% of the wetland. Polygons mapped with
the geomorphic component ‘R’ are rivers and streams and their adjacent valley bottoms.
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Results:
Based on the qualifier questions, approximately 138,156 acres of wetland in the study area
stabilize shorelines as a principal function. The total acres and percent of total wetland area
within the mapped area that meet the criteria for each qualifier question are found in Table 7.
Table 7. Mapping Results: Shoreline Stabilization
Shoreline Stabilization Criteria
Total Area Meeting Question Criteria (acres)
Is the wetland polygon mapped using the Riverine (R)
geomorphic component or immediately adjacent to a
stream, lake, or pond (adjacent to a polygon mapped
using the ‘LAKE’ map unit, a riverine polygon, or a
polygon mapped using a hydrologic component =1)?
Total
Total Area
Principally
Performing this
Function
(acres)
138,156
138,156
Percent of
Total
Wetland
Area
41.7%
41.7%
Map 7 below shows the results for this function; wetland areas shown in the green color have
been determined to stabilize shorelines as a principal function. All maps in this document are
available for download in a high resolution version at: http://cookinletwetlands.info/
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Map 7. Shoreline Stabilization
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BIO-GEOCHEMICAL FUNCTIONS
Sediment/Pollutant Storage
Wetlands can attenuate surface runoff, allowing the sediments, pollutants, and excess nutrients
carried in runoff to sink and be deposited in the wetland. Due to the slow movement of
sediment-laden water through wetland vegetation, across uneven ground surfaces, and
especially through pore spaces in peatlands sediments and other pollutants are retained. This
wetland functional process can preserve water quality in receiving waters downstream and
down-gradient aquatic systems. Wetlands with shallow gradients have a higher potential for
sediment retention than wetlands with steep gradients because flows can be slower and
retention time longer (Magee and Hollands 1998).
Some wetlands in the Mat-Su may actively receive pollutants such as sand, metals, and
petroleum products in runoff from adjacent impervious cover such as roadways and developed
areas. Wetlands may perform pollutant removal functions by receiving and storing toxicants
and immobilizing them by accumulation in fine grained mineral soils, organic soil layers, or via
plant uptake.
Although nutrient inputs from agricultural and other industrial sources are not high in the
Matanuska-Susitna Valley currently, the elevated amounts of nitrogen in global precipitation,
along with runoff from fields and lawns, contributes an increasing nutrient load to receiving
waters. Global industrial nitrogen fixation, mainly for use as fertilizer, now exceeds biological
fixation, and more than half of riverine loadings are now due to human activities (Gruber and
Galloway 2008). This nutrient loading, either from unfiltered run-off or the drainage of
peatlands, can lead to dead zones as oxygen is depleted by eutrophication in receiving waters.
Long-term retention of pollutants by wetlands can also result in the chemical transformation of
the retained sediments and toxicants. Heavy metals and hydrocarbons are often deposited
along with sediment when runoff enters a wetland. Once deposited, pollutants may be altered
biologically; they can be broken down by bacteria or taken up by plants and then incorporated
into accumulating peat when the plant dies. Toxicants can also be immobilized or chemically
converted to a less toxic form. This biological or physical entrapment of sediments and
toxicants is beneficial to aquatic life and downstream water quality. Where no wetlands occur,
these pollutants could be transported to a surface water system where they can impair both
public health and ecosystem health (Tilton, et al. 1997). Peatlands can serve as effective
sediment and toxicant traps for an extended period however, in order for them to remain
effective some remediation will eventually be required. While retention of pollutants may
degrade other wetland functions, retention can enhance the quality of downstream waterways
for organisms such as salmon, at least for a short time. In addition, the filtering capacity of
wetlands protects groundwater by removing contaminants before they seep into the aquifer
(Tilton, et al. 1997).
Possible indicators of this function in Mat-Su wetlands include features that slow water
movement, such as low-gradient peatlands, permeable moss surfaces, Sphagnum moss
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hummocks, tussocks, low inundated areas, and visible sediment deposits on the surface (Post
1996). Although it could be argued that nearly all wetlands have the capacity to perform this
function, there are indicators that could increase the likelihood that sediment or other
pollutants are introduced to a particular wetland. This includes conditions such as proximity to
roads, building pads, natural erosion features, mountainsides, agricultural or industrial areas,
and many other features where the opportunity for conveyance of sediments or pollutants is
greatest.
Peatlands are by far the most common wetlands in the Mat-Su, and peatlands can serve as
extremely effective sediment and pollutant traps because of their low gradient, and extremely
high volume of dead-end pore space, and potentially their high sorptive capacity (Reeve and
Slater 2002). All peatlands, therefore have the potential to perform the sediment/pollutant
retention function as a principal function. Additionally, peatlands that are actively receiving
storm water run-off from impervious surfaces are currently performing this function and thus
warrant heightened scrutiny to prevent degradation of that performance.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
sediment/pollutant retention as a principal function within the Mat-Su study area.
1) Is the wetland polygon on the State of Alaska's Impaired Water Bodies List or is the polygon
immediately adjacent to a location on the list (ADEC 2010)?
Notes: ADEC reports on the condition of Alaska’s waters to the U.S. Environmental Protection
Agency in the Integrated Water Quality Monitoring and Assessment Report (Integrated
Report). The Integrated Report contains the Impaired Water Bodies List and helps the State
prioritize waters for future data gathering, watershed protection, and restoration. All Clean
Water Act category (1-5) wetlands found in the Mat-Su and listed in the Integrated Report were
selected for this effort.
2) Is the wetland polygon adjacent to a road?
Notes: All wetland polygons that intersect a road or are within 75 feet of a road were selected.
These wetlands likely receive and detain storm water run-off and associated pollutants from
nearby impervious surfaces (Hewitt and Rashid 1990; Sutherland and Tolosa 2001; Backstrom
et al. 2003).
3) Is the wetland polygon mapped as a peatland in the CIC?
Notes: Peatlands are mapped using any of the following geomorphic components of the CIC:
Spring Fen (SF), Very Large Dune (VLD) Trough (RT), Headwater Fen (H), Depression (D),
Lakebed (LB), Drainageway (DW), Kettle (K), or Abandoned Meander Terrace (AMT). The large
volume of pore space and associated storage capacity typical of peatlands makes it possible for
these wetlands to retain sediment and associated pollutants from waters that flow through
them.
4) Is the wetland polygon mapped using the ‘DISTURB’ map unit or does the map unit name
have a ‘d’ suffix, or is the wetland a peatland adjacent to a ‘DISTURB’ map unit or polygon
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mapped using a ‘d’ suffix?
Notes: A wetland is classified as ‘DISTURB’ when its character cannot be discerned from the
present landscape or the landscape recorded on the aerial photography used for mapping.
Wetland units mapped as ‘DISTURB’ indicate that they are disturbed beyond recognition of
their natural character. Disturbed units can be created by a variety of human activities; the
most common activities in the Mat-Su are fill pads, road building, and gravel extraction. The
natural character of wetlands mapped with a ‘d’ suffix can be recognized, yet the wetland
contains a significant area disturbed by human activity. Peatlands adjacent to these wetlands
are likely performing the pollutant storage function because peatlands have extremely high
volumes of dead-end pore space.
5) Is the wetland polygon part of a complex adjacent to agricultural land?
Notes: All wetland polygons that are adjacent to agricultural lands that are designated as such
regardless of production status were selected. These wetlands likely could receive and detain
run-off containing fertilizers and other inputs such as animal waste that can create detrimental
nutrient loading leading to the potential for eutrophication problems in receiving waters.
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Results:
Based on the qualifier questions, approximately 253,403 acres of wetland in the study area
provide sediment and pollutant storage as a principal function. The total acres and percent of
total wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 8.
Table 8. Mapping Results: Sediment/Pollutant Storage
Sediment/Pollutant Storage Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function (acres)
Percent of Total
Wetland Area
Is the wetland polygon on the State of Alaska’s
Impaired Water Bodies List or is the polygon
immediately adjacent to a location on the list (ADEC
2010)?
9,882
Is the wetland polygon adjacent to a road (within 75
feet)?
73,611
Is the wetland polygon a peatland (mapped with the
geomorphic component ‘AMT’, ‘D’, ‘DW’, ‘K’, ‘H’, ‘LB’,
‘RT’, or ‘SF’) in the CIC?
193,994
Is the wetland polygon mapped using the ‘DISTURB’
map unit or does the map unit name have a ‘d’ suffix,
or is the wetland a peatland adjacent to a ‘DISTURB’
map unit or polygon mapped using a ‘d’ suffix?
1,231
Is the wetland polygon part of a complex adjacent to
agricultural land?
40,537
Total
253,403
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
2.9%
22.2%
58.6%
0.37%
12.2%
76.6%
wetlands
Map 8 below shows the results for this function; wetland areas shown in the green color have
been determined to store sediments / pollutants as a principal function. All maps in this
document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 8. Sediment / Pollutant Storage
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Nutrient Cycling and Storage
Nutrient availability, particularly nitrogen and phosphorous, is often the strongest limiting
factor for productivity of terrestrial and aquatic systems (Elser et al. 1990; Elser et al 2007).
This can be even more pronounced in northern latitudes where regulation of nutrients in
wetlands can play a critical role in ecosystem function (Chapin et al. 1978; Rouse et al. 1997;
Wyatt et al. 2010). Three processes can occur when nutrients reach wetlands, 1) the nutrients
can be removed by plant uptake, 2) they can be retained in sediments, or 3) they can be
transformed into different compounds.
Peatlands are particularly effective at trapping nitrogen (N) inputs. Inputs are both rapidly
removed by mosses and plants and transformed into gaseous forms in the oxygen-poor
environment of most peatlands. Conversely, if a peatland is drained, thus becoming more
oxygen-rich, large amounts of nitrogen that was previously retained in the peat can be released
downstream (Sikora and Keeny 1983).
The natural phosphorus (P) present in peatlands is rapidly recycled by plants. Additions of
phosphorous result in a small amount of removal by microbes and plants, and more is rapidly
released when plants die. Phosphorous can be further retained in the peat for only a few years
unless there is a high aluminum content, perhaps from volcanic ash in some areas. Peatlands
will not be as effective at longer-term phosphorous retention as mineral soils (Richardson
1985).
Potassium (K) is highly mobile, but nearly half of inputs to a black spruce bog in Minnesota
were retained in the bog (Veery and Timmons 1982). In the soil zone above permanent
saturation, potassium is tightly bound and recycled, but in the oxygen-deprived zones below it
is easily leached from the peat (Rydin & Jeglum 2006).
Wetlands may remove nutrients from water entering a site, incorporating them into plant
tissue and sometimes into the soil. Nutrients can enter wetlands in one form and leave in
another (transformation). Wetland productivity depends on inputs of organic matter and
nutrients; wetland systems in turn export organic matter and nutrients down-gradient (NWTC
1978). Most wetlands seem to act as nutrient traps, at least during the growing season. Periodic
inundation or overbank flooding into wetlands can allow decaying plant material to be washed
downstream to other aquatic ecosystems, where it supports the food web with energy and
nutrients.
Another factor affecting nutrient cycling is the differing biomass turnover rates between
vegetation strata. Deciduous shrubs turn over 34 to 43% of their biomass annually, adding a
substantial amount of litter to the soil surface (ADEC & USACE 1999). Shrubs recycle nutrients
effectively because tissue nutrient pools are high in proportion to biomass. The herbaceous
stratum produces new growth and senesces annually, decomposing more rapidly than woody
vegetation and thus cycling nutrients fairly rapidly. Mosses generally prohibit nutrient cycling
by acting as nutrient sinks; they rapidly intake nutrients and have slow rates of decomposition.
Wetland plant material may be consumed directly by vertebrates and invertebrates, or
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chemically and physically altered through decomposition before use by other consumers.
Decomposition and the rate at which nutrients are transformed to usable forms by plants
influence plant productivity and ultimately food chain dynamics. The rate of decomposition
and the degree to which nutrients and organic carbon are transported out of the wetland affect
the wetland’s role in the aquatic food chain. This is of particular importance in the Mat-Su in
relation to the many productive fish streams and downslope marine habitats of Cook Inlet.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
nutrient cycling and storage as a principal function within the Mat-Su study area.
1) Is the wetland complex large compared to its watershed?
Notes: For this landscape-scale functional assessment, large is defined in relation to a
sixth-order Hydrologic Unit Code (HUC) watershed as mapped by the U.S. Geologic Survey. In
watersheds the size of sixth-order HUCs, individual wetland polygons comprising 3% or more
of the watershed’s total area were considered large. This is based on methods for assessing
flow retention and flood control found in the Anchorage Wetland Assessment Method
(Appendix B, pg. 159) of the Anchorage Wetlands Management Plan (Municipality of
Anchorage, 1996), in which a point system is used to assign a score based on wetland area as a
proportion of watershed area. The maximum score is 25 points, from this maximum score a 15
point threshold (60% of maximum) was used to define large wetlands which correlates to the
3% of total area value for individual wetland polygons. Thus large wetlands have an
approximate size range of 300 – 1200 acres, based on the typical size range of 10,000 – 40,000
acres for USGS mapped sixth-order HUCs (NRCS 2010). In the Mat-Su Cook Inlet Classification
(CIC) mapping, contiguous large riverine wetland polygons, may sometimes extend outside
sixth order HUC boundaries. In these cases, the polygon was evaluated by only considering the
portion of the riverine wetland polygon within each HUC. Each of these percentages were
calculated and if any one portion of the polygon had a value of 3% or greater in relation to that
HUC then the entire polygon was attributed as ‘large’.
2) Is the wetland polygon mapped using the Riverine (R) geomorphological component of the
CIC?
Notes: Riverine wetlands are streams and their associated valley bottoms. Water in these
wetlands is frequently aerated, which facilitates the transformation of the nitrogen originating
in the peat into a form that many plants and animals can use (Rydin and Jeglum 2006; Klove
2001).
3) Is the wetland polygon a peatland and adjacent to a wetland mapped using the Riverine (R)
geomorphic component of the CIC?
Notes: Peatlands are mapped using any of the following geomorphic components of the CIC:
Spring Fen (SF), Very Large Dune (VLD) Trough (RT), Headwater Fen (H), Depression (D),
Lakebed (LB), Drainageway (DW), Kettle (K), or Abandoned Meander Terrace (AMT). Peatlands
sequester organic matter, which is rich in nutrients, especially nitrogen (Limpens, et al. 2006;
Rydin and Jeglum 2006; Clymo 1983). However, many of these nutrients are not in a form
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available for uptake by other organisms due to the anaerobic nature and low pH of peatland
porewater (Rydin and Jeglum 2006). Erosion of peat into adjacent streams and lakes with
aerated waters of higher pH makes the nutrients available. Increases in nitrogen from peat
eroding into receiving waters can even be large enough to cause eutrophication when peat is
mined (Klove 2001).
In the upper reaches of watersheds, where peatlands are often lacking, or in watersheds
without substantial cover of peat, alder may serve an important role in providing nitrogen, an
often limiting nutrient (Shafftel, et al. 2012). If remote assessment of the alder cover of a
watershed becomes possible, then identification of watersheds without peat, but with alder
could highlight additional Riverine wetlands also important in stream productivity.
Results:
Based on the qualifier questions, approximately 177,086 acres of wetland in the study area
provide nutrient cycling and storage as a principal function. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 9.
Table 9. Mapping Results: Nutrient Cycling and Storage
Nutrient Cycling and Storage Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function (acres)
Percent of
Total Wetland
Area
Is the wetland complex large compared to its
watershed?
10,899
Is the wetland polygon mapped using the Riverine (R)
geomorphic component of the CIC?
88,923
Is the wetland polygon a peatland (mapped with the
geomorphic component ‘AMT’, ‘D’, ‘DW’, ‘K’, ‘H’, ‘LB’,
‘RT’, or ‘SF’) AND adjacent to a wetland mapped using
the Riverine (R) geomorphic component of the CIC?
88,162
Total
177,086
Note: The sum of the qualifiers questions is greater than the total acres due
falling into multiple categories.
3.2%
26.8%
26.6%
53.5%
to wetlands
Map 9 below shows the results for this function; wetland areas shown in the green color have
been determined to provide nutrient cycling and storage as a principal function. All maps in
this document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 9. Nutrient Cycling and Storage
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BIOLOGICAL FUNCTIONS
Food Chain Support
The ability of a wetland to support the food chain can be defined as the relative abundance of
organic carbon available for use that is produced at or transported to a wetland (Klopatek
1988). Carbon-based (organic) molecules created by primary producers, mainly using the
energy from the sun, and the allochthonous materials transported to the wetland from outside
of it support the beginning of the food chain and lay at the center of the food web. By focusing
on the primary producers and allochthonous imports, problems with assessing food chain
support when dealing with more distant links in the food chain are resolved (Klopatek 1988).
Organic carbon molecules are frequently sequestered in the anaerobic environment of many
wetlands where the inefficiencies of decomposition in the absence of oxygen prevent their
immediate uptake. Instead, the carbon is slowly released into wetland porewaters where it is
exported down-gradient through a variety of surface and subsurface pathways to streams and
other receiving water bodies. This exported carbon is combined with other nutrients in order
to be assimilated by organisms in the more efficient aerobic environment of the receiving
waters (Shaftel et al. 2012; King et al. 2012).
Although some carbon is more easily assimilated by living organisms, there is probably little
difference in the quality or quantity of the organic carbon originating in the different peatland
types found in our area (Bedford et al. 1999, Fellman et al. 2008). However the assimilation of
the abundant carbon exported from peatlands will eventually become limited by the
availability of some other nutrient (usually N or P) according to the Sprengel-Liebig Law of the
Minimum (van der Ploeg et al. 1999). Peat has also been found to be a nitrogen source but it is
often in a form that is not bioavailable unless it enters an aerobic environment. Thus peatlands
that are adjacent to lakes or streams where they might undergo erosion and become
introduced to an aerobic environment can provide usable nutrients.
Another important local source of carbon and limiting nutrients is decomposing carcasses of
anadromous fish. Nutrients in these fish originate almost entirely outside of the wetlands but
are released to wetland plant and invertebrate communities by decomposition of the returning
fish. (Cederholm et al. 1989; Helfield & Naiman 2001; Wipfli et al. 1998). Although the adjacent
wetlands do not originally produce the marine-derived nutrients, the wetlands do uptake and
recycle these nutrients, and therefore likely support more complex food webs than they could
without them. There may be a positive feedback loop wherein the salmon carcasses provide
marine-derived nutrients supporting the adjacent plant and invertebrate communities, which
in turn provide for increased salmon production (Helfield & Naiman 2001).
Wetlands are in a position to directly export organic carbon if they are proximal to streams and
have hydraulic gradients that direct surface and subsurface flow to these streams.
Furthermore, wetlands adjacent to anadromous streams are more likely to be in a position to
uptake and recycle marine-derived nutrients imported by returning salmon.
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Methodology:
Below is a list of qualifiers that were used to select wetlands considered to perform food chain
support as a principal function within the Mat-Su.
1) Is the wetland polygon mapped as a peatland and immediately adjacent to a polygon
mapped with the Riverine (R) geomorphic component of the CIC?
Notes: Peatlands are mapped using any of the following geomorphic components of the CIC:
Spring Fen (SF), Very Large Dune (VLD) Trough (RT), Headwater Fen (H), Depression (D),
Lakebed (LB), Drainageway (DW), Kettle (K), or Abandoned Meander Terrace (AMT). Riverine
(R) polygons are rivers and streams and their associated valley bottoms. Due to the adjacency
to flowing water, water in these peatlands is frequently aerated, which facilitates the
transformation of the carbon and other nutrients originating in the peat into a form that many
plants and animals can use (Rydin and Jeglum 2006; Klove 2001).
2) Is the wetland polygon mapped as a peatland and immediately adjacent to a polygon
mapped using the ‘LAKE’ map unit of the CIC?
Notes: Peatlands are mapped using any of the following geomorphic components of the CIC:
Spring Fen (SF), VLD Trough (RT), Headwater Fen (H), Depression (D), Lakebed (LB),
Drainageway (DW), Kettle (K), or Abandoned Meander Terrace (AMT). Similar to peatlands
adjacent to riverine polygons those adjacent to lakes are in contact with water that typically
has higher dissolved oxygen facilitating the transformation of carbon and other nutrients in the
peat into a form that many plants and animals can use (Rydin and Jeglum 2006; Klove 2001).
3) Is the wetland polygon a peatland mapped with a hydrologic component of ‘1’ or adjacent to
such a polygon?
Notes: Peatlands are mapped using any of the following geomorphic components of the CIC:
Spring Fen (SF), VLD Trough (RT), Headwater Fen (H), Depression (D), Lakebed (LB),
Drainageway (DW), Kettle (K), or Abandoned Meander Terrace (AMT). Polygons mapped with
a hydrologic component of ‘1’ are ponds, this open water would have the same higher dissolved
oxygen properties as other forms of open water and thus facilitate transformation of nutrients
into an available form for plants and animals.
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Results:
Based on the qualifier questions, approximately 139,868 acres of wetland in the study area
provide food chain support as a principal function. The total acres and percent of total wetland
area within the mapped area that meet the criteria for each qualifier question are found in
Table 10.
Table 10. Mapping Results: Food Chain Support
Food Chain Support Qualifier Questions
Total Area Meeting Question Criteria (acres)
Is the wetland polygon a peatland (mapped with the
geomorphic component ‘AMT’, ‘D’, ‘DW’, ‘K’, ‘H’, ‘LB’,
‘RT’, or ‘SF’) AND immediately adjacent to a stream, lake,
or pond?
Total
Total Area
Principally
Performing
this Function
(acres)
139,868
139,868
Percent of
Total Wetland
Area
42.2%
42.2%
Map 10 below shows the results for this function; wetland areas shown in the green color have
been determined to support the food chain as a principal function. All maps in this document
are available for download in a high resolution version at: http://cookinletwetlands.info/
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Map 10. Food Chain Support
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Anadromous Fish Habitat
Many wetlands within the Mat-Su have the capacity to support anadromous fish (fish that are
hatched in fresh water, migrate into salt water for most of their lives, and then return to fresh
water to breed). It is important to note that this assessment will not predict habitat suitability
or occurrence accurately for every species. Fish species can be dependent on wetland habitats
for early development and rearing due to their relative cover, low water velocity, and
abundance of food sources. Wetlands with open water and ponds that are adjacent to
anadromous fish streams can provide important spawning and rearing habitat for fish species.
Wetlands with surface water present, a defined and consistent inlet and outlet, and moderate
vegetation interspersion are likely to provide fish habitat (Adamus Resource Assessment
1987); additionally, natural subterranean pipe systems likely play a role in peatlands (Holden
et al. 2002).
Many Mat-Su streams and their tributaries are anadromous fish streams. In Southcentral
Alaska, anadromous species of interest include Chinook salmon (Oncorhynchus tshawytscha),
chum salmon (O. keta), coho salmon (O. kisutch), pink salmon (O. gorbuscha), and sockeye
salmon (O. nerka), as well as Dolly Varden (Salvelinus malma). For the purpose of this method,
“anadromous streams” are defined as streams important to the spawning, rearing, or migration
of anadromous fish species. Mat-Su streams and adjacent wetlands provide vital freshwater
habitat and resources, affecting all life stages, for large populations of these fish.
Owing to their importance to Alaska’s economy, subsistence needs, and commercial and
recreational fishing, anadromous streams are protected under Alaska Statute 41.14.870, also
known as the Alaska Fish Act. Federal protection of fish habitat through the Magnuson-Stevens
Fishery and Conservation and Management Reauthorization Act of 2006 directs proponents of
federally-funded projects to consult with the National Marine Fisheries Service when any of
their activities may have an adverse effect on essential fish habitat. These laws protect against
adverse effects that may include direct (e.g., contamination or physical disruption), indirect
(e.g., loss of prey, or reduction in species' fecundity), site-specific or habitat-wide impacts,
including individual, cumulative, or synergistic consequences of actions.
Probably the most important considerations in assessing the capacity of a wetland to support
or improve downstream fish habitat is the proximity of the wetland to streams or waterbodies
and the presence of open water. Several GIS stream layers exist for the Mat-Su, which are used
to help determine whether Mat-Su wetlands support anadromous fish habitat. These include
polygon layers from the Mat-Su wetland mapping (Gracz 2013), line layers from the MSB GIS
database, USGS National Hydrography Dataset (NHD), the Mat-Su Basin Salmon Habitat
Partnership’s Salmon Watershed Atlas (2009), and the ADF&G anadromous stream mapping
(ADF&G 2013). Overall, stream data available for the MSB appears to be accurate enough for
this analysis, though field verification is necessary for streams not readily viewable in aerial
photos such as small streams and streams under forest along the Talkeetna Mountains, as field
observations have shown inaccuracies in some locations (Rice, personal observations). Recent
LiDAR and imagery is now available and work has begun to create a more accurate stream
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network spatial data layer (http://www.matsugov.us/it/gis/2011-lidar-imagery-project ).
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to provide
habitat for resident and anadromous fish as a principal function within the Mat-Su study area.
1) Is the wetland polygon intersecting an ADF&G-mapped anadromous fish stream?
Notes: ADF&G is responsible for maintaining anadromous waters data and the publication of
the Catalog of Waters Important for the Spawning, Rearing or Migration of Anadromous Fishes
and its associated Atlas. The Catalog and Atlas are updated each year as more current surveys
document the presence or absence of anadromous fish in waterbodies and nomination forms
are subsequently submitted to ADF&G. It is important to note that the ADF&G information on
the extent of anadromous fish habitat captures most large streams but does not capture most
small streams and springs in the Mat-Su and is regularly updated when new information
becomes available. The ADF&G anadromous stream data is delineated at a coarser scale and
often doesn’t match streams visible on aerial photography, but can contain more detailed small
stream data than the NHD.
2) Is the wetland polygon adjacent to a NHD-mapped stream that flows into an anadromous
fish stream?
Notes: NHD is the US Geological Service’s National Hydrography Dataset. The NHD offers the
most accurate and comprehensive GIS data available for streams, ponds, and lakes within the
MSB, though significant errors still exist. Accuracy problems do arise when trying to use the
NHD stream mapping in conjunction with the ADF&G anadromous stream data, which this
analysis has considered. The NHD dataset is more recent and more closely matches the actual
stream corridors visible on available aerial photography; however the GIS lines lack
anadromous fish information and do not capture all small streams.
3) Is the wetland polygon mapped using the Riverine (R) geomorphic component of the CIC or
does it lie adjacent to a Riverine polygon?
Notes: Riverine wetlands are rivers and streams and their adjacent valley bottoms. Gracz
(2013) utilizes Rosgen’s Stream Classification System (Rosgen and Silvey 1996) with some
modification in mapping these wetland types in the MSB.
4) Does the wetland polygon have a hydrologic code of ‘1’ and is it adjacent to a polygon
mapped using the Riverine (R) geomorphic component of the CIC?
Notes: Wetlands with a hydrologic code of 1 indicate a wetland that has surface water present
all year over at least 10% of the wetland. For this landscape-based assessment, the study team
determined that these wetlands most likely have the highest probability of having or
supporting flow pathways through which juvenile fish can pass. Riverine wetlands are river
and stream reaches and their immediately adjacent valley bottoms. (See notes under #1
above.)
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Results:
Based on the qualifier questions, approximately 202,649 acres of wetland in the study area
provide anadromous fish habitat as a principal function. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 11.
Table 11. Mapping Results: Anadromous Fish Habitat
Anadromous Fish Habitat Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function
(acres)
Percent of
Total Wetland
Area
Is the wetland polygon mapped as an anadromous fish
stream by ADF&G?
86,584
Is the wetland polygon adjacent to a NHD mapped
stream that flows into an anadromous fish stream?
8,950
Is the wetland polygon mapped using the Riverine (R)
geomorphic component of the CIC or does it lie
adjacent to a Riverine polygon?
197,878
Does the wetland polygon have a hydrologic code of ‘1’
and is it adjacent to a polygon mapped using the
Riverine (R) geomorphic component of the CIC?
4,697
Total
202,649
Note: The sum of the qualifiers questions is greater than the total acres due
falling into multiple categories.
26.1%
2.7%
59.8%
1.4%
61.2%
to wetlands
Map 11 below shows the results for this function; wetland areas shown in the green color have
been determined to support or contribute anadromous fish habitat as a principal function. All
maps in this document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 11. Anadromous Fish Habitat
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Habitat for Maintenance of Biodiversity
Because different organisms are adapted to different conditions, wetlands supporting a wider
array of physical conditions adjacent to each other likely support higher species richness than
wetlands of more uniform composition. A small peatland in an ice-block depression with a
central pond progressively ringed by bands of sedges, shrubs, and forest probably supports
greater biodiversity than a hummocky peatland in a depression that only supports shrubs and
sedges. A large patterned peatland on a relict lakebed probably supports greater biodiversity
than a large uniformly forested peatland on the same landform.
The diversity of habitat structure, both in the horizontal and vertical dimensions, has long been
known to be at least as important in supporting biodiversity as the particular species present
(Rotenberry and Weins 1980). Diverse habitat structure can create more options for more life
stages of more individuals in more species. For example, if diverse physical conditions are
adjacent to one another, then the richness of food sources is likely greater, creating more
options in times of scarcity. More habitat options can potentially support higher species
richness and numbers than where uniform conditions limit the number of food sources
creating the potential for greater biodiversity.
Ponds, streams and lakes provide essential habitat for the many species that rely on open
water for some portion of their life cycle. Many insects are entirely aquatic, moose feed on
aquatic plants, frogs breed in ponds, many ducks feed in ponds or lakes, and fish spawn in
streams. The greatest biodiversity is probably present when wetlands with a high
heterogeneity of physical environments are also adjacent to open water.
In the Cook Inlet Classification (CIC), wetland polygons mapped as containing more hydrologic
components should support more diversity than wetlands mapped with only one or two
hydrologic components. For example, the small peatland described above, with a central pond
ringed by sedges, shrubs, and forest, could be mapped as ‘K1-4’. The geomorphic component ‘K’
indicates that the wetland is a peatland in an ice-block depression, and the ‘1-4’ indicates that
hydrologic components 1, 2, 3 and 4 are all present at a scale too fine to delineate at 1:18,000.
Hydrological component ‘1’ indicates the small pond, hydrological component ‘2’ indicates
sedges, the ‘3’ for shrubs and the ‘4’ for forest. This peatland will likely support greater
biodiversity than a similarly-sized peatland mapped as supporting only shrubs and sedges
(‘K32’). The adjacency of the central pond should produce even greater biodiversity because so
many organisms rely on open water for some portion of their life history. Likewise, wetland
polygons mapped with more than one hydrologic component that are adjacent to a lake or
stream should support greater biodiversity than those mapped using only a single hydrologic
component, or those not adjacent to a lake or stream.
Methodology:
While many of the characteristics mentioned above influence the biodiversity of a wetland, it
may be impossible to approach an actual value for the total biodiversity of any wetland without
numerous intense and time-consuming field studies. For that reason, proxies are used for this
function (listed below).
1) Is the wetland polygon mapped with more than two hydrologic components of the CIC?
Note: Hydrologic components are numeric (ranging 1-6) and reflect the position and variation
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in water levels in a wetland. Lower-numbered components (1 or 2) are used when water levels
are less variable and closer to the surface; higher numbers indicate greater variability and
generally deeper water tables. Polygons mapped with more than two components are patchy at
a scale too fine to map at 1:18,000, indicating a heterogeneous habitat structure, which may
support greater biodiversity.
2) Is the wetland polygon mapped with two hydrologic components and is it adjacent to a
polygon mapped using the Riverine (R) geomorphic component of the CIC, or the ‘LAKE’ map
unit, or a polygon mapped with the hydrologic component number ‘1’?
Note: The presence of two components indicates a moderately heterogeneous habitat
structure. In the CIC the hydrologic component ‘1’ is a pond. Adjacency of a moderately
heterogeneous wetland to a stream, lake, or pond increases its structural complexity by adding
open water, a habitat type required by many organisms. The increased complexity should
support greater biodiversity.
More heterogeneous polygons, those with greater than two hydrologic components, are
covered above, under criterion (1).
3) Is the wetland polygon mapped using the ‘LBSF’, ‘RC’ or ‘DWR’ map units of the CIC?
Note: ‘LBSF’ is the map unit representing large patterned peatland complexes on relict glacial
lakebeds. ‘RC’ is a Riverine component designating river or stream reaches with cut banks,
point bars and a well-developed flood plain. ‘DWR’ represents heterogeneous peatlands formed
in relict glacial drainageway features. These three wetland types support diverse vertical and
horizontal habitat heterogeneity, which should support increased biodiversity. Many also
contain open water.
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Results:
Based on the qualifier questions, approximately 196,264 acres of wetland in the study area
provide habitat for biodiversity or maintain biodiversity as a principal function. The total acres
and percent of total wetland area within the mapped area that meet the criteria for each
qualifier question are found in Table 12.
Table 12. Mapping Results: Habitat for Maintenance of Biodiversity
Habitat for Maintenance of Biodiversity Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function
(acres)
Is the wetland polygon mapped with more than two
hydrologic components of the CIC?
62,666
Is the wetland polygon mapped with two hydrologic
components and is it adjacent to a polygon mapped using
the Riverine (R) geomorphic component of the CIC, or the
‘LAKE’ map unit, or a polygon mapped with the hydrologic
component number ‘1’?
152,688
Is the wetland polygon mapped using the ‘LBSF’, ‘RC’ or
‘DWR’ map units of the CIC?
22,958
Total
196,264
Note: The sum of the qualifiers questions is greater than the total acres
falling into multiple categories.
Percent of
Total
Wetland
Area
18.9%
46.1%
6.9%
59.3%
due to wetlands
Map 12 below shows the results for this function; wetland areas shown in the green color have
been determined to provide habitat opportunities that support biodiversity. All maps in this
document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 12. Habitat for Maintenance of Biodiversity
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Habitat for Species of Concern
Wetlands provide habitat for many species of fish, wildlife, plants, and other organisms for at
least some portion of their life cycle. Occurrence of a species in a wetland can confirm
suitability of habitat whereas absence does not necessarily confirm unsuitability because all
suitable habitat may not be occupied. Therefore, wetlands with habitat characteristics suitable
for a species could potentially support that species even though the species may not occur
there today.
Species of concern are defined here as those ranked on the Alaska Natural Heritage Program’s
tracking list as S3 or lower. Plants ranked as S3 are rare and at moderate risk of extirpation
(Table 1). Birds ranked as S3 are “vulnerable” (Alaska Natural Heritage Program 2013,
NatureServe 2013). Currently the only species on the lists ranked as S3 or lower with ranges in
Mat-Su freshwater wetlands are plants and birds.
Table 13. State conservation rank definitions for plants from the Alaska Natural Heritage
Program (2014).
Rank
S1
Definition
Critically imperiled within the state; at very high risk of extirpation because of very few
occurrences, declining populations, or extremely limited range and/or habitat
S2
Imperiled within the state; at high risk of extirpation because of few occurrences,
declining populations, limited range, and/or habitat
S3
Rare within the state; at moderate risk of extirpation because of restricted range, narrow
habitat specificity, recent population decline, small population sizes, a moderate number
of occurrences
Known occurrences of rare plants are inventoried in the Alaska Natural Heritage Program’s
(AKNHP) BIOTICS Data Portal (http://aknhp.uaa.alaska.edu/maps/biotics/). AKNHP keeps
specific site survey records and survey range estimates of rare plants. Approximately 354 rare
vascular plants are currently listed and tracked by the AKNHP in Alaska. Eight plant species on
the list could occur in freshwater wetland habitats within the MSB (Natural Heritage Program
2014a). Potential wetland habitat for each species was determined by reviewing the species
descriptions in regional floras (Table 14). Plants unlikely to occur in wetlands were omitted.
During field surveys, both green-keeled cottongrass and star sedge were collected or recorded
at several locations. Note that these selections were made based on the availability of spatial
data to AKNHP, whereas additional species are of concern to other entities. For example, the US
Fish and Wildlife Service and Audubon both maintain lists of species of concern that should be
applied when assessing wetland function at specific sites.
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Table 14. State-ranked S3 or lower plants intersecting Mat-Su wetlands. Habitat descriptions
are from the regional floras of Hulten (1968), Scoggan (1978), Welsh (1974), and Brayshaw
(1985).
Scientific Name
Blymus rufus
Common Name
Red clubrush
Rank
S1
Habitat
Tidal flats or freshwater peatlands
Carex lenticularis v. Goose-grass sedge
dolia
Carex parryana
Parry sedge
S3
Muskeg, lakeshores, gravel bars
S1
Tidal flats, marshes, lake margins
Cicuta bulbifera
S2
Marshes, bogs, swamps, wet
thickets
Tidal flats, marshes, fens
Water hemlock
Glyceria striata var. Fowl mannagrass
stricta
Potamogeton
Pondweed
obtusifolius
Eriophorum
Green-keeled
viridicarinatum
cottongrass
Carex echinata
Star sedge
ssp. echinata
S2
S2/S3
S2
Shallow lakes and ponds with
organic sediment bottoms
Peat bogs, wet meadows, marshes
S1/S2
Bogs, wet places
Three bird species on the list have been documented in the MSB and could require wetlands for
some part of their life cycle (AKNHP 2014a): tule white-fronted goose (S1/S2-breeding), rusty
blackbird (S3-non-breeding), and northern saw-whet owl (S3). The tule white-fronted goose
breeds near wetland ponds or lakes, the rusty blackbird is associated with wetland forest, and
the saw-whet owl uses wetland forest edge habitat, especially adjacent to rivers (Cornell Lab of
Ornithology 2014).
Methodology:
Potential occurrence was balanced with documented occurrence when selecting wetlands
capable of supporting species of concern as a principal function. The species and their
occurrences were obtained by using the Alaska Natural Heritage Program’s BIOTICS data portal
(AKNHP 2014a), except for star sedge, and some green-keeled cottongrass, which were
collected while mapping. The BIOTICS portal documents locations of tracked species as
polygons. Polygons are buffered by the reliability of location data. To select polygons, the Cook
Inlet Basin was first broadly defined then polygons for all species with rank equal to S3 or
greater concern and lying within the Basin were selected. Polygons that did not intersect with
any freshwater wetlands mapped in the MSB were eliminated.
Within the occurrence polygons, wetland polygons meeting habitat criteria were identified for
each species by matching habitat descriptions given in regional flora (plants) or by the Cornell
Lab of Ornithology (2014) (birds) to the mapping units in the Cook Inlet Classification (Table
15). For each species, wetland polygons that intersected an occurrence polygon of a species
from the BIOTICS portal and met the species-specific criteria in Table 15 were selected. For the
green-keeled cottongrass, the polygons in which this plant was recorded while mapping were
also selected. For the star sedge, only the polygons where it was recorded during mapping
were selected.
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1) For any species listed in Table 15, does the wetland polygon intersect with an occurrence
polygon and meet the criteria?
Table 15. Species, habitat, and selection criteria for the species of concern. The selection
criteria are based on the Cook Inlet Classification and are used for wetlands intersecting the
occurrence polygons of each species. The occurrence polygons were obtained through the
Alaska Natural Heritage Programs BIOTICS data portal (AKNHP 2014a).
Species
Habitat
Wetland polygons meeting habitat
criteria
Blymus rufus
Tidal flats or freshwater
peatlands
Mapped with the geomorphic
components: Depression (D),
Drainageway (DW), Headwater Fen (H),
Kettle (K), Lakebed (LB) , VLD Trough
(RT), or Spring Fen (SF) (the freshwater
peatlands)
Carex lenticularis
v. dolia
Muskeg, lakeshores, gravel
bars
All wetlands in occurrence polygon
Carex parryana
Tidal flats, marshes, lake
margins
Mapped with hydrologic component ‘1’,
’2’ (marshes) or adjacent to a ‘LAKE’
Cicuta bulbifera
Marshes, bogs, swamps,
wet thickets
All wetlands in occurrence polygon
Glyceria striata
var. stricta
Tidal flats, marshes, fens
All wetlands in occurrence polygon
Potamogeton
obtusifolius
Shallow lakes and ponds
with organic sediment
bottoms
Wetland polygons mapped with the
geomorphic component = Kettle (K) or
Lakebed (LB) AND hydrologic
component = 2; OR
where recorded during mapping
Eriophorum
viridicarinatum
Peat bogs, wet meadows,
marshes
Wetlands where this plant was recorded
during mapping
Carex echinata
ssp. echinata
Bogs, wet places
Wetlands where this plant was recorded
during mapping
PLANTS
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Table 15. (cont.)
Species
Habitat
Wetland Polygons meeting habitat
criteria
BIRDS
Tule white-fronted Wetland ponds and lakes
goose
Wetland mapped with hydrologic
component = 1 (ponds); OR
Wetlands adjacent to a ‘LAKE’
Rusty blackbird
Forested wetlands
Wetlands mapped with the
geomorphologic component =
Depression (D), Headwater Fen (H),
Kettle (K), VLD Trough (RT), or Spring
Fen (SF) AND the hydrologic component
= 4; OR
Wetlands mapped as Lakebed (LB) AND
hydrologic component = 6; OR
Wetlands mapped as Drainageway (DW)
AND hydrologic component = 5A; OR
Wetlands mapped with the Discharge
Slope geomorphic component (S) &
containing vegetation component =
birch (B), white (G), Lutz (L), Black (M),
or Sitka (P) spruce (forested wetlands)
Northern
saw-whet owl
Forest edge, stream
margins
Wetlands mapped with the
geomorphologic component =
Depression (D), Headwater Fen (H),
Kettle (K), VLD Trough (RT), or Spring
Fen (SF) AND the hydrologic component
= 4; OR
Wetlands mapped as Lakebed (LB) AND
the hydrologic component = 6; OR
Wetlands mapped as Drainageway (DW)
AND with the hydrologic component =
5A; OR
Wetlands mapped with the discharge
Slope geomorphic component (S) &
containing the vegetation component =
birch (B), white (G), Lutz (L), Black (M),
or Sitka (P) spruce; (forested wetlands)
AND
that are adjacent to a polygon not
meeting the criteria. (forest with a
non-forest edge); OR
Wetland polygons mapped using the ‘RC’
map unit
(RC have forest-stream edges)
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Results:
Based on qualifier questions, approximately 271,463 acres of wetland in the study area provide
habitat for species of concern as a principal function. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 16.
Table 16. Mapping Results: Habitat for Species of Concern
Habitat for Species of Concern Qualifier Questions
Total Area Meeting Question Criteria (acres)
Does the wetland polygon provide habitat for a species
listed in Table 15?
Total
Total Area
Principally
Performing this
Function
(acres)
271,463
271,463
Percent of
Total
Wetland
Area
82.0%
82.0%
Map 13 below shows the results for this function; wetland areas shown in the green color,
notably all mapped wetlands, likely support suitable habitat for the species identified in this
section. All maps in this document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 13. Habitat for Species of Concern
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HUMAN IDENTIFIED VALUES
Recreation
Borough residents value open space, including wetland areas, for recreational opportunities
(MSB 2005). This wetland value considers the suitability of the wetland and associated water
courses to provide recreational opportunities. Hunting, fishing, trapping, and other similar
recreational opportunities are evaluated separately under the “Consumptive uses” value and
are not considered here.
Many of the recreational values of Mat-Su wetlands are associated with trail use. According to
the MSB Recreational Trails Plan, approximately 2,000 miles of regionally significant
recreational trails cross much of the Borough. These trails provide for a wide range of
functional and recreational activities, including, but not limited to hiking, skiing, biking,
boating, canoeing, bird watching, dog mushing, all-terrain vehicle travel, and snowmobiling. It
should be noted that many commonly used trails within the MSB are not dedicated. While some
of these undedicated trails lie entirely on public lands, the MSB (2008) estimates that
approximately 80 percent of the trails cross private land. Important to this methodology,
winter trails are often routed through open wetlands, where low-growing vegetation is covered
in snow; offering widespread areas of recreational use outside of a traditional trail corridor.
The MSB has mapped and maintains a GIS layer showing officially recognized trails in the
Borough.
Another set of recreational values of Mat-Su wetlands are associated with lakes, rivers, and
other watercourses. Borough residents and visitors frequently boat, water ski, use personal
water craft, and canoe along Mat-Su waterways during the summer. In winter, recreationists
skate on frozen lakes and use frozen rivers and creeks as snow machine and dog sled
thoroughfares. Nearly 35 lakes in the Borough have individual lake management plans adopted
by the MSB Assembly which list the important lake values and specify allowable lake activities.
Wetlands in the MSB are also valued for bird and other wildlife viewing. Wildlife viewing is
valued so much by residents that one of the policies of the MSB Comprehensive Development
Plan Update (MSB 2005) is to preserve opportunities for people to observe and enjoy wildlife
and wildlife habitats (Policy PO2-2). According to the USFWS (2003), 36% of all Alaskans
participate in bird watching. Birding is also important to the State’s economy; more than 40
percent of the total birders in Alaska come from elsewhere.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
recreation as a principal wetland value within the Mat-Su study area.
1) Is the wetland polygon within 1/4 mile of a recreational facility?
Notes: Public facilities, including public boat launches, campgrounds, public use cabins, and
libraries, are mapped as points on the MSB’s Public Use Facilities GIS layer.
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2) Is the wetland polygon within an area managed for recreation?
Notes: Areas managed for recreation are mapped using the MSB’s Special Land Use District
GIS layer. Special land use districts, parks, and lake management areas are included in this
layer.
Lake management areas within the MSB include:
Big Lake
Blodgett Lake
Bonnie Lake Area
Upper Bonnie Lake
Bonnie Lake
Carpenter Lake
Christiansen Lake
Crooked Lake
Crystal Lake
Diamond Lake
Florence Lake
Fish Lake
Honeybee Lake
Island and Doubloon Lake
Island Lake
Doubloon Lake
Jean Lake
John Lake
Knik Lake
Lake Five and Unnamed Lake
Lake of the Woods
Liten Lake
Little Lonely Lake
Long Lake (Houston)
Marilee Lake
Marion Lake
Memory Lake
Morvro Lake
Neklasen Lake
Lower Neklasen Lake
Paradise Lake
Question Lake
Little Question Lake
Rainbow Lake
Ravine Lake
Shirley Lake
Stevens and Oriana Lakes
Three Mile Lake
Toad Lake
Twin Island Lake
Walby Lake
West Papoose Lake
Whiskey Lake
Wolf Lake
Wolverine Lake
3) Is the wetland polygon within a designated state park or refuge?
Notes: State parks, refuges, and recreational areas are mapped using a GIS layer created by the
Alaska Department of Natural Resources. The major refuges in the assessment area are: Palmer
Hay Flats State Game Refuge and Goose Bay State Game Refuge. Recreation areas include: Little
Susitna Recreation River, Knik Sled Dog and Recreation District, and Matanuska Valley Moose
Range
4) Is there boat use associated with the wetland?
Notes: In addition to wetlands adjacent to lakes with management plans covered in question 2,
‘R’ wetland polygons are riverine ecosystem wetlands including rivers and streams and their
adjacent valley bottoms, these wetlands where they are associated with 2D streams in the NHD
dataset are presumed to be large enough to support recreational boat use.
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5) Is the wetland polygon within one mile of a mapped trail?
Notes: Trails are mapped using the MSB’s Official Trails GIS layer which was derived from the
MSB Trails Plan and the DNR trails layer (Alaska Trails 1:63,360). .
Results:
Based on the qualifier questions, approximately 251,565 acres of wetland in the study area
provide opportunities for recreation as a principal value. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 17.
Table 17. Mapping Results: Recreation
Recreation Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function
(acres)
Percent of
Total
Wetland
Area
Is the wetland polygon within ¼ mile of a recreational
facility?
16,206
Is the wetland polygon within an area managed for
recreation?
68,561
Is the wetland polygon within a designated state park or
78,308
refuge?
Is there boat use associated with the wetland?
89,780
Is the wetland polygon within one mile of a mapped trail?
161,974
Total
251,565
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
4.8%
20.7%
23.6%
27.1%
48.9%
76.0%
wetlands
Map 14 below shows the results for this value; wetland areas shown in the green color have
been determined to support recreation as a principal value. All maps in this document are
available for download in a high resolution version at: http://cookinletwetlands.info/
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Map 14. Recreation
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Consumptive Use
Consumptive opportunities consume or utilize the plants, animals, or other resources that are
intrinsic to an area. In the Mat-Su, the primary consumptive uses of wetlands are sport (or
recreational) fishing, hunting, and trapping. Plant gathering and berry picking are also
important.
Sport fishing is an important consumptive activity occurring in waters maintained by natural
Mat-Su wetlands. The Mat-Su, which falls within ADF&G’s Northern Cook Inlet Management
Area, supports extensive and diverse recreational fisheries for all species of Pacific salmon. The
three most sought-after salmon species are the Chinook, coho, and sockeye salmon. The area
also supports excellent fishing opportunities for wild stocks of rainbow trout, Dolly Varden,
Arctic grayling, and northern pike and limited opportunities for burbot, arctic char, and lake
trout. Eighty area lakes are stocked annually with rainbow trout, arctic grayling, arctic char,
and landlocked coho and Chinook salmon (ADF&G-Sport Fish 2014a). Important sport fishing
rivers in the area include the Little Susitna River which has the second-largest freshwater
harvest of silver salmon in Alaska and receives over 40,000 angler-days of use annually
(ADF&G Sport Fish 2014b&c).
Sport fishing is important to the local and state economy. A 2007 statewide assessment of the
economic contribution of sport fishing in Alaska estimated that 475,534 resident and
nonresident licensed anglers fished 2.5 million days in Alaska and spent nearly $1.4 billion on
licenses and stamps, trip-related expenditures, pre-purchased packages, and equipment and
real estate used for fishing. The $1.4 billion of angler spending in Alaska in 2007 resulted in
economic activity that supported 15,879 jobs, provided $545 million of income, and resulted in
$123 million in state/local tax revenues. Most anglers spend money in the Southcentral region.
Notably, much of Southcentral’s economic activity centers on the Cook Inlet area, partly
because Anchorage and the Mat-Su are large population centers with good fishing nearby. In
2007, in the Cook Inlet subregion which includes the Mat-Su, about $733 million was spent by
anglers, which supported 8,056 jobs and generated $55 million in state and local taxes (ADF&G
2007). Habitat is crucial to the survival of healthy fisheries, and good fish habitat is maintained
by natural wetlands.
Sport hunting is another important consumptive use occurring in Mat-Su Study Area wetlands.
The Borough falls within ADF&G Game Management Units (GMU) 14A, 14B, and 16A and
portions of GMU 13A, B, D, E, and 16B. Waterfowl hunting particularly is associated with
wetland areas. Also, currently, there are bull moose permit and open season hunts in most of
the GMUs within the Mat-Su Study Area. There are general season hunts for black bear and wolf
in all of the Borough GMUs and open season hunts for brown bear in every Borough GMU
except for 14B. There are drawing permit hunts for bull caribou in GMU 14B (western
Talkeetna Mountains) and general season hunts for bull caribou in GMU 16A and 16B. Hunting
is specifically permitted within the Hay Flats Recreational Area Special Land Use District
(Borough code 17.08.130) and the Knik Sled Dog and Recreational Special Land Use District
(Borough code 17.20.040). Although hunting is not specifically called out by MSB code in any
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other area, it is permitted throughout the Borough. Local regulations, ordinances, or state park
rules may prohibit hunting and access to lands, and it is the responsibility of the hunter to
check with the landowner.
Hunting is a key consumptive use of Mat-Su wetlands because it contributes to the local and
state economy directly through the sale of hunting licenses and indirectly through money spent
on travel, lodging, equipment, and supplies. To many households, hunting provides meat for
the winter. For others, hunting is an important recreational and social activity.
Another consumptive use of Mat-Su wetlands is trapping. Trapping for furbearers, including
beaver, red fox, lynx, martin, mink, weasel, muskrat, river otter, wolves, coyote, and wolverine,
is permitted in all Borough GMUs during the winter months (open season varies with species).
Trapping is regulated by ADF&G Division of Wildlife Conservation, and trappers must purchase
a trapping license. Trapping is permitted throughout the Borough and specifically permitted
within the Knik Sled Dog and Recreational Special Land Use District (Borough code 17.20.040);
however, ADF&G trapping regulations request that trappers “avoid high recreational use areas
and avoid situations where domestic dogs or cats may be caught, such as near homes or trails
frequently used by hikers, skijorers, dog mushers, or other people.”
Trapping is an important consumptive use within Mat-Su wetlands because it contributes to
the local and state economy directly through the sale of trapping licenses and the buying and
selling of furs. Trappers earn money by selling pelts and this income is multiplied through the
local economy by their purchases. To some residents, trapping is also an important
recreational activity.
Berry picking and medicinal and edible plant gathering are additional important consumptive
uses occurring in Mat-Su wetlands. According to the MSB Coastal Management Plan (2006),
berry picking is popular in the Hatcher Pass public use area and along the Glenn Highway
National Scenic Byway. Although not publically documented, medicinal and edible plant
gathering is also important.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
consumptive use as a principal value within the Mat-Su.
1) Is the wetland polygon situated on public lands or part of a stocked lake or recreational
river?
Notes: Public lands such as State parks, refuges, and recreational areas are mapped using a GIS
layer created by the Alaska Department of Natural Resources (DNR). The MSB also has a GIS
layer showing MSB-owned public lands. The approximately 130,000 acre Matanuska Valley
State Moose Range was created by the Alaska State Legislature in 1984 to maintain, improve,
and enhance moose populations and habitat and other wildlife resources of the Mat-Su area,
and to perpetuate public multiple use of the area. The DNR manages the area in cooperation
with ADF&G.
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2) Does the wetland polygon include a fish stream or support fish habitat?
Notes: This question addresses the opportunity for wetlands to support anadromous or
resident populations of fish. Polygons with a hydrologic component = 1, or mapped using the
Riverine (R) geomorphic component; or those polygons immediately adjacent to one mapped
using a Riverine (R) geomorphic component, a ‘LAKE’ map unit, or intersected by a stream
were selected. A hydrologic component equal to 1 indicates a wetland that has surface water all
year over at least 10% of the wetland (an indication of ponding). Riverine (R) wetlands are
streams and their associated valley bottoms.
3) Is the wetland polygon immediately adjacent to a ‘LAKE’ map unit in the CIC?
Notes: Lakes and adjacent undeveloped lands are popular areas for accessing fishing,
waterfowl hunting, and trapping opportunities in the Mat-Su.
4) Is the wetland polygon mapped as a Discharge Slope (S) in the CIC with a willow vegetation
component (map units: SAS, SCS, SGS, SMS, SS, SSA, SSC, SSG, SSM, SLS, or SSL)?
Notes: These wetlands, due to the dominate willow vegetation are considered important for
moose winter browse in the Mat-Su study area.
5) Is the wetland polygon in a known moose wintering area mapped by ADF&G?
Notes: In 2005, ADF&G digitized moose habitat areas from the Alaska Habitat Management
Guides (AHMG). Maps falling in the Cook Inlet basin were included and taken from the AHMG,
Southcentral Region, Volume I, “Distribution and Human Use of Mammals”. Definitions and
sources are found in the AHMG Atlas. Map scale is 1:250,000.
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Results:
Based on the qualifier questions, approximately 296,654 acres of wetland in the study area
provide opportunities for consumptive use as a principal value. The total acres and percent of
total wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 18.
Table 18. Mapping Results: Consumptive Uses
Consumptive Uses Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function
(acres)
Percent of
Total
Wetland
Area
Is the wetland polygon situated on public lands or part of
a stocked lake or recreational river?
90,017
Does the wetland polygon include a fish stream or
support fish habitat?
244,752
Is the wetland polygon immediately adjacent to a ‘LAKE’
map unit in the CIC?
16,388
Is the wetland polygon mapped as a Discharge Slope (S) in
the CIC with a willow vegetation component?
214
Is the wetland polygon in a known moose wintering area
mapped by ADF&G?
205,532
Total
296,654
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
27.2%
73.9%
4.9%
0.06%
62.1%
89.6%
wetlands
Map 15 below shows the results for this value; wetland areas shown in the green color have
been determined to support consumptive uses as a principal value. All maps in this document
are available for download in a high resolution version at: http://cookinletwetlands.info/
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Map 15. Consumptive Uses
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Education
Some wetlands serve as sites for “outdoor classrooms.” According to the 2005 MSB
Comprehensive Development Plan Update, Borough residents value the natural environment,
including wetlands, for the opportunities it provides for education (MSB 2005). Many MSB
schools use nearby wetlands to teach children about nature and science. Children’s groups visit
the Spring Creek Farm Environmental Learning Center in Palmer and learn about wetlands and
other natural habitats. In addition, the University of Alaska Fairbanks operates the Palmer
Center for Sustainable Living at the Matanuska Experiment Farm, which is part of the
Agriculture & Forestry Experiment Station. The Palmer Hay Flats State Game Refuge and the
Dale Saunder’s Crane Sanctuary are also established locations for educational opportunities
specifically focusing on wetlands.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
education as a principal wetland value within the Mat-Su.
1) Is the wetland polygon within a parcel with a school or within 1/10 mile of a school?
Notes: School sites were mapped using MSB’s Parcel GIS Layer.
2) Is the wetland polygon a known educational site for any age group?
Notes: Educational sites are determined through input from stakeholders and the public.
Included in this assessment are the Spring Creek Farm Environmental Learning Center
managed by Alaska Pacific University, the Palmer Center for Sustainable Living managed by the
University of Alaska, Palmer Hay Flats State Game Refuge and the Dale Saunder’s Crane
Sanctuary.
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Results:
Based on the qualifier questions, approximately 9,197 acres of wetland in the study area
provide opportunities for education as a principal value. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 19.
Table 19. Mapping Results: Education
Education Qualifier Questions
Total Area Meeting Question Criteria (acres)
Is the wetland polygon within a parcel with a School or
within 1/10 mile of a school?
Is the wetland polygon a known educational site for any
age group?
Total
Total Area
Principally
Performing this
Function
(acres)
Percent of
Total
Wetland
Area
75
0.02%
9,121
9,197
2.7%
2.7%
Map 16 below shows the results for this value; wetland areas shown in the green color have
been determined to support educational uses as a principal value. All maps in this document
are available for download in a high resolution version at: http://cookinletwetlands.info/
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Map 16. Education
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Visual Quality/Aesthetics
Most Mat-Su residents value the importance of protecting natural environment visual quality
and aesthetics, including wetlands. The Borough’s Comprehensive Development Plan Update
states that the natural environment, including wetland areas, provides many valuable
amenities such as scenic landscape, community identity, and open space (MSB 2005). The Big
Lake Comprehensive Plan (2009) states that residents value the Big Lake natural environment
for its natural beauty, dark night skies, and natural quiet and that retaining the landscape to
reflect the natural beauty of the land, minimizing light pollution, and noise pollution is a public
priority. The Meadow Lakes Comprehensive Plan (2005) states that public open space,
waterways, and trails are important and the “natural feel” of the community and the dominate
sense of natural landscapes – forests, wetlands, streams, wildlife, and views-should be retained.
Other area MSB plans mirror these statements.
The beauty of natural areas, including wetlands, attracts visitors to the Mat-Su. The Mat-Su
includes 24 state park units and is in close proximity to Denali National Park and Preserve.
There are more than 20 public campgrounds in the Mat-Su and 17 remote cabins are available
for use. The approximate annual volume of all visitors to the Borough was estimated to be
nearly 780,000 visitors in 2006/2007. Total spending in the Mat-Su by all visitor markets was
estimated at $201 million for the full year period of May 2006 to April 2007. Of this amount,
$80 million (40 percent) is attributable to out-of-state visitors and $121 million (60 percent) to
in-state visitors (McDowell Group 2008). While not all visitors are drawn to the Mat-Su because
of wetlands aesthetics, it is likely that wetlands help to make the natural environment a place of
beauty that attracts visitors.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
visual quality and aesthetics as a principal value within the Mat-Su study area.
1) Is the wetland polygon adjacent to a road?
Notes: All wetland polygons that intersect a road or are within 50 feet of a road were selected
for this effort. This qualifier selects wetland polygons that are readily viewable to people while
driving.
2) Is the wetland polygon adjacent to one mapped with the ‘LAKE’ map unit in the CIC or is it a
wetland mapped with the Riverine (R) geomorphic component such that there is boat use
associated with the wetland?
Notes: Wetlands mapped as adjacent to ‘LAKE’ map units have a potential combination of uses
including boat or float plane traffic or cabins. Wetland polygons mapped using the Riverine
geomorphic component (R) include rivers and streams and their adjacent valley bottoms, these
wetlands where they are associated with 2D streams in the NHD dataset are presumed to be
large enough to support boat use. This qualifier selects wetland polygons that are readily
viewable to people due to their adjacency to open water.
3) Is the wetland polygon within one mile of a mapped trail?
Notes: Trails are mapped using the MSB’s Official Trails GIS layer which was derived from the
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MSB Trails Plan and the DNR trails layer (Alaska Trails 1:63,360). This qualifier selects wetland
polygons that are readily viewable to people while accessing trails.
Results:
Based on the qualifier questions, approximately 155,242 acres of wetlands in the study area
provide visual quality and aesthetics as a principal value. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 20.
Table 20. Mapping Results: Visual Quality and Aesthetics
Visual Quality and Aesthetics Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function
(acres)
76,073
Percent of
Total
Wetland
Area
Is the wetland polygon adjacent to a road (within 50 ft.)?
Is the wetland polygon adjacent to one mapped with the
‘LAKE’ map unit in the CIC or is it a wetland mapped with
the Riverine (R) geomorphic component such that there is
boat use associated with the wetland?
108,323
Is the wetland polygon within one mile of a mapped trail?
161,974
Total
155,242
Note: The sum of the qualifiers questions is greater than the total acres due to
falling into multiple categories.
22.9%
32.7%
48.9%
46.9%
wetlands
Map 17 below shows the results for this value; wetland areas shown in the green color have
been determined to have visual quality or aesthetics as a principal value. All maps in this
document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 17. Visual Quality and Aesthetics
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Cultural and Historic Importance
Some wetlands in the Mat-Su support activities that are important to local tribes. In addition,
some Mat-Su wetlands are important in the history of Alaska and are considered to have
cultural and historic value. Throughout their history the Dena’ina Athabascan, including the
Tyonek, Knik, Chickaloon, and Eklutna tribes, have placed a great deal of value on their family
ties and their ties to the land and water where their traditional resources originate. To this day,
the physical and natural environment, including wetland areas, remain highly valued to tribes.
Salmon and moose continue to be harvested in Mat-Su wetland areas by local tribal members.
Wetlands are also important berry picking places for tribal members. Although today there is
no state or federally-recognized subsistence in the Mat-Su, the Cook Inlet Dena’ina harvest local
resources, and depend on them both economically and culturally (KABATA 2004).
Under AS 05 Alaska Administrative Code (AAC) 93.200, the Knik Tribal Council and Native
Village of Eklutna Tribes are entitled to harvest salmon for personal consumption under
educational fishery programs. The Knik Tribal Council uses an educational fishery site on the
west side of Knik Arm near Fish Creek. The Native Village of Eklutna uses a site on the east side
of Upper Cook Inlet. Reported harvest levels for the educational fisheries are 500 salmon for
the Knik Tribal Council (ADF&G Permit SF 2005-101) and 1,000 salmon for the Native Village
of Eklutna (ADF&G Permit SF 2005-133).
Later in history, the Mat-Su was explored by Russians, and then inhabited by miners and
trappers. A wetland may have historic value if it is the location of a historically significant site,
structure, or activity. For example, the Iditarod National Historic Trail runs through many
wetland areas in the Mat-Su on its way to Nome, and areas near rivers and streams may have
been historically used by placer miners.
Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to have a
cultural and historic importance as a principal value within the Mat-Su.
1) Is the wetland polygon within one hundred feet of the Historic Iditarod Trail?
Notes: Wetlands near the Historic Iditarod Trail may help to keep the character of the trail.
2) Is the wetland polygon within one mile of a site listed in the National Register of Historic
Places (NRHP)?
Notes: The following historic sites are listed on the NRHP within the study area: Bailey Colony
Farm (AHRS Site No. ANC-056); Berry House (AHRS Site No. ANC-202); Cunningham-Hall Pt-6,
Nc-695W (AHRS Site No. ANC-131; Herried House (AHRS Site No. ANC-198); Hyland Hotel
(AHRS Site No. ANC-485); Knik Site; Matanuska Colony Community Center (AHRS Site No.
ANC-750); Palmer Depot; Patten Colony Farm (AHRS Site No. ANC-472); Puhl House (AHRS Site
No. ANC-197); Rebarchek, Raymond, Colony Farm (AHRS Site No. ANC134); St. Michael Roman
Catholic Church; Teeland Country Store (AHRS Site No. ANC-114); Trych, Blanche, and Oscar
House (AHRS Site No. ANC-00764); United Protestant Church (AHRS Site No. ANC-248); Wasilla
Community Hall (AHRS Site No. ANC-135); Wasilla Depot (AHRS Site No. ANC-0088); Wasilla
Elementary School (AHRS Site No. ANC-110); and the Whitney Section House (AHRS Site No.
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ANC-00044).
Additional Note: Because culturally important wetlands are sensitive to disturbance, and to
respect the wishes of the first inhabitants of the Cook Inlet area (and because the locations of
cultural resources is protected by law), this document does not map individual wetlands that
are important Alaskan Natives in the area. Instead, the Tyonek, Knik, Ekultna, and Chickaloon
Tribes should be contacted to determine if wetlands are important for personal/subsistence
use on a project-by-project basis. Also, the MSB’s Cultural Resources Division and historical
societies should be contacted to determine whether there are any special concerns or interests
in the wetland area on a project by project basis.
Tyonek Tribe
1689 C Street, Suite #219
Anchorage, AK 99501-5131
Phone: 907-272-0707
Website: http://www.tyonek.com
Knik Tribe
901 West Commercial Drive
Wasilla, AK 99654
Phone: 907-373-7991
Website: http://www.kniktribalcouncil.org/
Eklutna Tribe
26339 Eklutna Village Rd.
Chugiak, AK 99567
Phone: 907-688-6020
Website: http://www.eklunta-nsn.gov/
Chickaloon Village Traditional Council
P.O. Box 1105
Sutton, AK 99674
Phone: 907-745-0749
Email: [email protected]
MSB Cultural Resources Division
350 E. Dahlia Ave.
Palmer, AK 99645
Phone: 907-745-9859
Website:
http://www.matsugov.us/planning/divi
sions/cultural-resources
Palmer Historical Society
P.O. Box 1935
Palmer, AK 99645
Email: [email protected]
Website:
http://www.palmerhistoricalsociety.org/index.
htm
Alpine Historical Society
P.O. Box 266
Sutton, AK 99674
Phone: 907-745-7000
Email: [email protected]
Website:
http://www.alpinehistoricalpark.org/
Wasilla-Knik Historical Society
300 N. Boundary Street, Suite B
Wasilla, AK 99654
Phone: 907-376-2005
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Results:
Based on the qualifier questions, approximately 23,375 acres of wetland in the study area are
culturally and historically important as a principal value. The total acres and percent of total
wetland area within the mapped area that meet the criteria for each qualifier question are
found in Table 21.
Table 21. Mapping Results: Cultural and Historic Importance
Cultural and Historic Importance Qualifier Questions
Total Area Meeting Question Criteria (acres)
Total Area
Principally
Performing this
Function
(acres)
Percent of
Total
Wetland
Area
Is the wetland polygon within 100 feet of the Historic
Iditarod Trail?
12,025
3.6%
Is the wetland polygon within one mile of a site listed in
the NRHP?
11,435
3.4%
Total
23,375
7.0%
Note: The sum of the qualifiers questions is greater than the total acres due to wetlands falling
into multiple categories.
Map 18 below shows the results for this value; wetland areas shown in the green color have
been determined to have cultural or historical significance as a principal value. All maps in this
document are available for download in a high resolution version at:
http://cookinletwetlands.info/
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Map 18. Cultural and Historic Importance
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Mat-Su Wetland Functions and Values
Landscape Level Assessment Methodology and Mapping
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Uniqueness
Wetlands that are regionally rare or unique may be considered to have value over more
common types of wetlands. For this assessment, a wetland considered unique is "worthy of
being considered in a class by itself, extraordinary." A Mat-Su wetland may be unique if it is
significantly different from other wetlands in the area or requires additional protection. These
wetlands can provide habitat essential for the conservation of rare species or possess
significant biological, geological, or other features that are locally rare. A wetland can also be
unique because it is performing an important function that other nearby wetlands do not
perform.
Three types of wetlands found in the Mat-Su basin that each make up only a small proportion of
the overall wetland area are ripple trough wetlands, spring fens and headwater fens. Ripple
trough wetlands are peatlands that only occurs within the linear transverse valleys found in the
Meadow and Beaver Lakes area (Gracz 2013). These unique landform features are believed to
have been created by glacially influenced mega-flood events that produced a series of large,
flow-transverse ridges of unconsolidated deposits. These underlying deposits may drive
groundwater flow patterns in the Meadow and Beaver Lakes area, likely adding to the creation
of the Mat-Su ripple trough wetlands (Wiedmer et al. 2010). Of the 330,815 acres of wetlands
currently mapped in the Mat-Su study area, ripple trough wetlands cover 4,136 acres, or only
1.3 percent of mapped wetlands in the Mat-Su study area.
Spring fen wetlands are small peatlands surrounded by uplands (Gracz 2013). This wetland
type has unique ecological and hydrological characteristics not typically observed in other
Mat-Su wetlands; notably, spring fens are groundwater through-flow sites where groundwater
is discharged along the upslope boundary of the wetland and recharged back into the ground
along its downslope boundary. This brief surface contact of groundwater often creates nutrient
rich conditions for plants, animals, and microorganisms. Nutrients are typically released into
the groundwater by weathering along subsurface flow paths and are made available for uptake
when discharged to the surface. This transmission is known to have a strong ecological effect in
plant species health and diversity (Eriksson 1984). Spring fen wetlands comprise only 2,645
acres, or 0.8 percent of all mapped wetlands.
Headwater fen wetlands are an uncommon type of peatland occupying the headwaters of
first-order streams. Due to their location in the upper watershed, the hydrologic linkage to
downstream aquatic environments, and the relative small size and number of this type in the
Mat-Su, headwater fen wetlands are considered unique. Additionally, this wetland type
performs a higher number of principal wetland functions than most other mapped Mat-Su
wetlands perform. Headwater fen wetlands comprise only 603 acres, or 0.18 percent of
mapped wetlands in the Mat-Su study area.
Wetlands that provide habitat for rare species can also be considered unique. In addition to the
rare plants identified in the Alaska Natural Heritage Program’s BIOTICS data portal that have
occurrences in Mat-Su basin wetlands through the course of this mapping effort as part of
ground-truthing the mapping results a range expansion for the species, Coptis aspleniifolia,
was documented and this wetland has been specifically included under this function.
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Methodology:
Below is a list of qualifiers that were used to select or exclude wetlands considered to perform
uniqueness as a principal value within the Mat-Su study area.
1) Is the wetland polygon mapped using the Spring Fen (SF), Very Large Dune Trough (RT), or
Headwater Fen (H) geomorphic component of the CIC?
Notes: These types of wetlands have biological, geological, or other features that are locally
rare or unique.
2) Has a rare plant been documented within the mapped wetland polygon?
Notes: Known occurrences of rare plants are inventoried in the Alaska Natural Heritage
Program’s (AKNHP) BIOTICS Data Portal (http://aknhp.uaa.alaska.edu/maps/biotics/).
AKNHP keeps specific site survey records and survey range estimates of rare plants. For this
assessment, plants considered rare in Alaska are defined as species having a rank of S1
(critically imperiled in Alaska), S2 (imperiled in Alaska), or S3 (rare or uncommon in Alaska).
Approximately 354 rare vascular plants are currently listed and tracked by the AKNHP in
Alaska. As described in Table 14 (see pg. 56), only eight species have been identified by AKNHP
within the Mat-Su study area.
Results:
Based on the qualifier questions, approximately 8,147 acres of wetland in the study area have
uniqueness as a principal value. The total acres and percent of total wetland area within the
mapped area that meet the criteria for each qualifier question are found in Table 22.
Table 22. Mapping Results: Uniqueness
Uniqueness Qualifier Questions
Total Area Meeting Question Criteria (acres)
Is the wetland mapped using the Spring Fen (SF), VLD
Trough (RT), or Headwater Fen (H) geomorphic
component of the CIC?
Has a rare plant been documented within the mapped
wetland polygon?
Total
Total Area
Principally
Performing this
Function
(acres)
Percent of
Total
Wetland
Area
7,384
2.2%
763
8,147
0.2%
2.4%
Map 19 below shows the results for this value; wetland areas shown in the green color have
been determined to be unique features in the Mat-Su. All maps in this document are available
for download in a high resolution version at: http://cookinletwetlands.info/
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Map 19. Uniqueness
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