Ephemeral Streams in the
Texas Blackland Prairie Region
Ryan Blankenship, AWB
[email protected]
Dallas, TX 972.770.1312
Jason Claudio-Diaz, P.E., CFM
[email protected]
Charlotte, NC 704.954.7464
Agenda

Texas Blackland Prairie Eco-Region
•
•
•
•

Eco-region Introduction
Ecological Attributes
Consequences of Intensive Management
Jurisdictional Determination Challenges
Case Study
•
•
•
•
•
Hydrology
Bankfull Determination
Local/Regional Curves
Effects of Drought on Hydrology
Design Issues
Texas Blackland Prairie Eco-Region
Timeline of Events
1850
1880

1910
1930
1940 1950
1960
Current Land Use
• 10% Urban
• 70% cultivated row crops
• 20% tame pasture
• <1% prime blackland prairie grassland
Current
Future?
Ecological Attributes

Climate
•
•
•
Precipitation average of 35-inches with extremes from 22-inches to 55-inches
Temperature average 45°F to 85°F with extremes from 0°F to 115°F
HIGHLY variable, HIGH intensity, LOW frequency, LOW duration storm events
January 10, 2013
January 30, 2014
August 7, 2013
August 30, 2012
January 30, 2014
January 10, 2013
Ecological Attributes

Vegetation
•
•
Few Mature Woody Species
Forage and Cover
• Graminoids
–
–
–
–
Switchgrass (Panicum virgatum)
Indiangrass (Sorghastrum nutans)
Big bluestem (Andropogon gerardii)
Little blustem (Schizachyrium
scoparium)
• Forbs
• Holding capacity of soil and
water from root systems
Ecological Attributes

Hydrology
•
Altered Hydrological Regime?
Swale?
Ephemeral with Intermittent Pools
Intermittent with Perennial Pools
Hydrology increasing: water source and flow duration
Ephemeral
Intermittent
Perennial
Ecological Attributes

Soils
•
•
•
Upper Cretaceous marine chalks,
limestone, shale
Deep, dark gray to black alkaline
clays
“cracking clays”
0 – 6-inches
Very dark gray (10YR 3/1) clay
Firm when moist, very plastic when wet
6 – 16-inches
Very dark gray (10YR 3/1) clay
Very firm when moist, very plastic when wet
• High shrink-swell property
16 - 40-inches
Dark olive gray (5 YR 3/2) clay
When dry cracks extend into this subsoil layer
40 - inches +
dark olive gray (5Y 3/2) clay
with few olive (5Y 5/4) and reddish-yellow (7.5YR 6/8) specks
Parent material
Weathered chalk, calcareous clay, clayey shale
Houston Black clay soil series
Consequences of Intensive/Sustained Land Practices

Velocity of a rain drop
•
•
Soil compaction
Soil decomposition/consistence
• Loose, friable, firm
•
•
Topsoil lost, leaving subsoil
Infiltration rates
• Erositivity of clay soil types
• Compounded by less frequent, higher intensity rain events
May 13, 2014
August 13, 2013
Consequences of Intensive/Sustained Land Practices
January 21, 2013
December 10, 2013
Jurisdictional Determination Challenges
Is it a stream?
Should it be a stream?
Will it be a stream?
Jurisdictional Determination Challenges
Historic OHWM?
Current OHWM?
Jurisdictional Determination Challenges
Historic OHWM?
Current OHWM?
Current OHWM?
Historic OHWM?
Jurisdictional Determination Challenges
Historic OHWM?
Current OHWM?
Hydrology

Harmel, Richardson, King, and Allen. “Runoff and
soil loss relationships for the Texas Blackland
Prairies ecoregion.” Journal of Hydrology (2006)
331, 471-483
• Created for watershed management practices, water supply
modeling and need for hydraulic calculations
• Hydrologic data collected since 1937
• pre-1970 stage by hand, post-1970 automated
• 2 – 100 yr peak flow estimated from 14 smaller watershed and
3 larger USGS watersheds
• 0.005 – 6.8 mi2 Riesel Lab (NRCS), 309 – 965 mi2 USGS
• Seasonal variation in runoff amounts
• Watershed size and annual peak runoff relationship
• Land use and runoff relationships
Seasonal Variation in Runoff


Dry, Saturated, Field Capacity, and
Transition Phases
June – September
• 28% annual rain
• 14% annual runoff

April – May
• 23% annual rain
• 29% annual runoff
Watershed Size and Peak Discharge

Study divided at 54 ha or ~0.2 mi2
• Baird 1950 suggested everything
over 54 ha was overestimated


Lack of well-defined drainage
channels leads to greater
percentage of flow reaching the
outlet after the peak
Loss of excess appreciable
precipitation due to the surface
cracking of soils
• More pronounced in small
watersheds and shorter Tc
Rainfall near Dallas/Ft. Worth
Year
Annual Precip
Above/Below Average
2013
29.40
-3.5
2012
31.26
-1.7
2011
25.88
-7.0
2010
31.70
-1.2
2009
40.89
8.0
2008
27.10
-5.8
2007
50.05
17.1
2006
29.75
-3.2
2005
18.97
-14.0
2004
47.57
14.6
2003
24.55
-8.4
Land Use and Runoff Relationships




1949 – 1965
Native Prairie vs. Traditional Management
No significant difference in precipitation
Traditional Management
• +56% runoff
• +100% peak flow
Bankfull
Local/Regional Curves
Local/Regional Curves
Bankfull Area (ft2)
100.0
10.0
1.0
0.01
y = 16.563x0.6181
R² = 0.9551
y = 19.417x0.7095
R² = 0.9295
0.1
Drainage Area (mi2)
1
10
Design Issues

Dry vs. Wet seasons
• Soil surface cracking
• Saturated clay vs. highly mobile loose material
• Separate nested channels?


Affects of the long-term drought
Hydrologic response (drainage area)
• Separate curves/design data to adjust for smaller DA’s




Vegetation type and success
Grade control
In-stream habitat
Construction timing
• Temporary stabilization
Contacts and Acknowledgements:

Jason Claudio-Diaz, P.E., CFM
Kimley-Horn | 2000 South Boulevard, Suite 440, Charlotte, NC 28203
Direct: 704 954 7464 | Mobile: 919 271 9381 | http://www.kimley-horn.com/surface-water-resources

Ryan Blankenship, Associate Wildlife Biologist®
Kimley-Horn | 12750 Merit Drive Suite 1000 Dallas, Texas 75251
Direct: 972 770 1312 | Main: 972 770 1300| www.kimley-horn.com
Rosewood Ennis, LLC
Wetlands Management