Floods and Levees
Upper Mississippi River Conference
Oct 13, 2016
Sally McConkey, P.E., CFM, D. WRE
Universe of Levees
FEMA Objective:
Level of Protection
Communicate the most
current information for
flood insurance
purposes.
NFIP & USACE
NFIP only
Area represents all levees throughout the US.
100-year
USACE Objective:
Assess all levees in
USACE programs,
regardless of level of
protection.
No nexus with
USACE only
NFIP or USACE
Federal
O&M
1
USACE
built /
Local
O&M
2
Local
built /
Enrolled
in RIP
Local
3
4
Levee Categories
FEMA & Levees

Main Question: does the levee meet the FEMA
standards to accredit the levee (levee system) as
providing protection during a 1% annual chance
event?

Plain English: Is the area behind (“protected”) by
the levee considered in the 1% annual chance
floodplain and thus subject to floodplain
management and insurance requirements?

NOTE: the 1% annual chance flood is a thresh hold
for floodplain management and insurance NOT a
safety standard.
FEMA & Levees

Accredited Levee

Levees owned and operated by federal agency OR local
public institution (community, levee district, …)

Proof of construction meeting 44CFR 65.10 standards

Operation and Maintenance Plan

Accreditation = proof of construction, maintenance, and
sufficient height ≠ a performance guarantee

Provisionally Accredited Levees (PAL) – levee is shown as

Levee Analyses and Mapping Procedure (LAMP)
providing protection from the 1% annual chance flood event,
the flood hazard in the levee protected area is shown as
shaded Zone X, notes on the map provide specifics
Procedures for
Assessment of Reaches
of a Levee System:
• Sound Reach
• Freeboard Deficient
• Overtopping
• Structural Based
Inundation
• Natural Valley
LAMP
Leveed Area
Illinois River Levees: Sizing Up Their
Impact on Flooding and Risk
Levee and
Drainage Districts
Akanbi, A.A., Y. Lian, and T.W. Soong. 1999. Illinois State Water Survey Contract Report 645.
Flood Management Options on Illinois River

If just 14% of the floodplain along a 200-km reach of the Illinois River
were utilized to store flood crests, an additional 44% of the floodplain
would gain protection from a 100-year flood. Akanabi et al. (1999)

Even greater gains from relatively small areas might be possible if
flood conveyance, rather than just flood storage, were provided.
Akanabi, A.A., Y. Lian, and T.W. Soong. 1999. Illinois State Water Survey Contract Report 645.
Naturalizing
Floodplains
Hydraulic, Ecological and
Economic Effects of
Reconnecting Rivers with
Their Floodplains
Changwoo Ahn, George Mason University
Ecologist
Misganaw Demissie, Illinois Water Survey
Engineer
Andrew Isserman, University of Illinois at Champaign-Urbana
Economist
Douglas Johnston, Iowa State University
Geographer
Yanqing Lian, Illinois Water Survey
Engineer
Zorica Nedovic-Budic, University of Illinois at Champaign-Urbana
Planner
Richard Sparks, National Great Rivers Research & Education Center
Ecologist
David White, Agricultural Watershed Institute
Economist
Reconnecting regulated rivers with their
floodplains
Conclusions from a reports prepared by a
multidisciplinary team funded by the National
Science Foundation and The Nature Conservancy.
That depending on scale; national, regional or
local;
reconnecting rivers with their floodplain can:

Reduce flood damages

Increase natural goods and series and

Potentially contribute to economy.
100%
In the state of Illinois:
90%
80%
1. Cropland in Illinois
River floodplain is only 2%
of total cropland.
70%
2. Public lands & waters
in floodplain were
privatized and drained,
1880s-1920s. Before
then, these floodplains
produced fish. Now they
produce corn.
40%
60%
50%
30%
20%
10%
0%
Cropland in
Illinois River
Floodplain
Cropland
Outside
Floodplain
Levee effects upon flood levels: an empirical assessment
Heine, R. A. and Pinter, N. (2012), Hydrol. Process., 26: 3225–
3240. doi:10.1002/hyp.8261
Hydrological Processes
Volume 26, Issue 21, pages 3225-3240, 18 JAN 2012 DOI:
10.1002/hyp.8261
http://onlinelibrary.wiley.com/doi/10.1002/hyp.8261/full#hyp82
61-fig-0006
1993 Flood
Reducing Risk
(consequences X frequency of exposure)