Hydrology arid
Flood Control

Wetlands are
transition zones
between uplands
and deeper
water, unique
ecosystems char-
acterized by their
hydrology, soils
and vegetation.
They function like
natural tubs,
storing flood
waters that over-
flow riverbanks
and surface
water that col-
lects in depres-
sional  areas. In
this way, wet-
lands can help
protect adjacent
and downstream
property from
flood damage.
                          Wetlands:   Protecting Life  and
                          ^fHil    Property from  Flooding
                   The Federal Emergency Management Agency (FEMA) states that
                  floods are the most common and widespread of all natural dis-
                   asters—except fire.  Most communities in the United States
                   have experienced some kind offloading. FEMA encourages
                   the use of wetlands for stormwater detention in lieu of, or in
                   conjunction with, traditional structural flood control measures.
                   (Source: FEMA)
How Do Wetlands Help Reduce

The effectiveness of wetlands for flood abatement
may vary, depending on the size of the area, type
and condition of vegetation, slope, location of the
wetland in the flood path and the saturation of wet-
land soils before flooding.  A one-acre wetland can
typically store about three-acre feet of water, or one
million gallons.  An acre-foot is one acre of land,
about three-quarters the size of a football field, cov-
ered one foot deep in water. Three acre-feet
describes the same area of land covered by three feet
of water. Trees and other wetland vegetation help
slow the speed of flood waters. This action, com-
bined witli water storage, can actually lower flood
heights and reduce the water's destructive potential.
(Source: EPA)

The Wetlands Initiative completed an 18-month
study, "Flood Damage Reduction  in the Upper
Mississippi River Basin: An Ecological Means." The
study revealed that restoring the 100-year flood zone
of the Upper Mississippi five-state watershed could
store 39 million acre-feet of floodwater, the volume
that caused the Great Flood of 1993, and save over
$16 billion in projected flood damage costs.

In Minnesota, an additional study by The Wetlands
Initiative noted that flood peaks and damage costs
would be decreased by restoring die natural hydrol-
ogy of the floodplain. The cost of replacing the
flood control function of the 5,000 acres of wet-
lands drained each year in Minnesota alone would
be $1.5  million, compared to the potentially mil-
lions of dollars lost to flooding. Preserving wetlands
in the first place and restoring some of those that
have been drained could help reduce future flood
losses. (Source: The Wetlands Initiative)
                                                               Preserving and protecting
                                                               coastal wetlands can help
                                                               reduce storm damage.
                                                               St. Stanislaus was a boy's
                                                               Catholic Boarding School
                                                               over a hundred years old in
                                                               Bay St. Louis, MS.  Located
                                                               on the beach overlooking
                                                               the Gulf, it was destroyed
                                                               by Hurricane Katrina. This
                                                               picture was taken before
                                                               the building disintegrated.

   W     h
t      I     a
are Helping

These studies and
others indicate
that wetlands
may play a part
in flood abate-
ment. The fol-
lowing examples
illustrate how
across the coun-
try are restoring
wetlands in order
to reduce the
threat and costs
of flood damage.
Charles River, Massachusetts

  Along the Charles River in Massachusetts, the
  U.S. Army Corps of Engineers (the Corps) has
  acted to utilize wetlands in preventing flood
  damage.  It was calculated that loss of all wetlands
  in the Charles River watershed would have caused
  an average annual flood damage cost  of $ 17
  million. The Corps concluded that conserving
  wetlands was a natural, less expensive solution to
  controlling flooding than the construction of
  dikes and dams alone, and they proceeded to
  acquire 8,103 acres of wetlands in the Charles
  River basin for flood protection.  (Source: U.S.
  Army Corps of Engineers - Charles River Natural
  Valley Storage Area)

Horseshoe Park,  Colorado

 In 1982, an earthen dam on Lawn Lake in Rocky
 Mountain National Park collapsed, suddenly
 releasing almost 700 acre-feet  of water into the
 Roaring River. A wall of water 25 to 30 feet high
 moving at 9 miles per hour rushed downstream
 and entered Fall River at Horseshoe Park. The
 Park contained wetlands adjacent to the river, with
 meadow grasses, reed and dense willow stands.
 Here the flood wave spread across the broad, flat
 valley and was slowed by wetland vegetation. The
 height of the wall of water  was reduced to about
 10 feet, and the water spread out  over the meadow
 to a width of 1,300 feet. The flood was finally
 contained by Olympus Dam on Lake  Estes, but it
 had claimed 4 lives and caused $31  million in
 damage. If not for the wetlands and meadows  at
 Horseshoe Park, the damage would have been
 much worse.  The height and speed of flood waters
 In 1982 these meadows and wetlands at Horseshoe Park in
 Colorado were hit by a 25 to 30 foot wall of water. The height
 and speed of the flood waters were reduced by the wetland
 vegetation, and the damaging flood peak was greatly reduced.
             were reduced by the wetland vegetation, and tr
             damaging flood peak was greatly reduced. (Sou
             Jarrett and Costa 1984)

            Grand Kankakee Marsh, Indiana

             In 1900, the Kankakee Marsh was one of the
             largest, most ecologically diverse wetlands in th
             United States. During the 20th century much
             the mairsh was drained and converted to
             agricultural use. Channelization of the Kankaki
             River, which fed the marsh, reduced its length
             from 250 to 90 miles. As a result, water qualit
             was degraded and flooding increased. An
             ambitious project was undertaken  to address th
             concerns. The project, featuring diverse partne
             from all levels of government, private conservat
             groups and business, was designed to restore ov
             25,000 acres of wetlands. With a grant from th
             Nordi America Wetlands Conservation Act anc
             donations of cash and land, 3,000 acres of
             wetlands have already been restored. Waterfowl
             populations have increased, water quality is
             improving and flooding  has decreased. (Source:
             National Park Service, "Floods, Floodplains anc
             Folks", 1996, U.S. Fish and Wildlife Service,
             Private Lands Office)

            Mayview Wetland Project, Pennsylvania

             The Pennsylvania Department of Transportatio
             (DOT)  completed a wetland restoration projec
             offset impacts to 32 acres of wetlands that were
             filled during the construction of Interstate 279
             through Southwestern Pennsylvania and the
             Southern Expressway. The site of the wetland
             restoration  is Mayview, a 65-acre piece of land,
             flanking Chartiers Creek, a major  stream. The
             creek v/as subject to frequent, high velocity
             flooding and constructing wetlands there is
             helping control these floods. The  new wetland;
             provide flood storage capacity for 63 million
             gallons of water and serve as an outdoor classro
             for nearby schools.  The Department of
             Transportation is seeking funding  to restore
             additional acreage. (Source: National Park Serv
             "Floods, Floodplains and Folks", 1996)

            Prairie  Wolf Slough, Illinois

             The Middle Fork of the  North Branch of the
             Chicago River flows through an abandoned fari
             field in  the suburbs.  The area was identified as
             future location for a trail, part of the North

Help       ing
 Branch of the Chicago River Open Space Plan designed
 by the Friends of the Chicago River and Lake County
 Stormwater Management Commission, a regional open
 space advocacy organization. By restoring wetlands
 hydrology, clearing non-native vegetation and planting
 wetland, prairie and savanna vegetation, the functions and
 values of the wetlands have been restored. Structures used
 to drain die area for farming were removed, and a new water
 control structure was constructed to decrease sedimentation
 of the river. The result was moderation of stormwater flows
 which provided the area widi flood protection, as well as
 permanent open space and new environmental education
 opportunities. (Source: National Park Service, "Floods,
 Floodplains and Folks", 1996, Friends of the Chicago River)

Vermillion River, South Dakota

 The Vermillion River has always flooded. It has a narrow
 channel and flows slowly, making it "flood prone."
 Thousands of years ago, this part of South Dakota was
 scoured by glaciers that carved out shallow depressions
 which remain today and seasonally fill with water.  These
 "prairie potholes" are intermittent, seasonal wetlands which
 dot the landscape. They quickly thaw in spring and provide
 habitat for a multitude of migratory birds and other water

 For hundreds of years, die rain and snow melt in the
 watershed were held in these wetlands, and runoff across the
 prairie was slowed. As South Dakota became populated,
 many prairie potholes were filled to facilitate farming.
 While these wetlands are small,  they are numerous and can
 hold a significant amount of flood water. As more wetlands
 were filled, flooding increased.

 The Great Flood of 1993 was devastating to the area.  To
 combat future flooding, structural flood controls were put
 in place, but they were not sufficient. In response to this
 problem, the National Park Service and the Federal
 Emergency Management Agency formed a partnership with
 the South Dakota Division of Emergency Management and
 Turner-Lincoln-Clay Counties Water  Project District.
 Working together, this coalition assessed the area and
 condition of the remaining network of podioles. They
 developed a plan to protect the remaining wetlands and
 restored some of those that had  been filled.
 (Source: National Park Service, "Floods, Floodplains and
 Folks", 1996, The Vermillion River: Managing the
 Watershed to Reduce Flooding,  Federal Emergency
 Management Agency)
         The Special Case of Coastal
         Wetlands in many locatiot
         protection. Nowhere is this function more important than along
         coastal areas. Coastal areas are vulnerable to hurricanes and
         other powerful storms, and the fiat coastal terrain means that
         land and property can be exposed to the full power of these
         storms. Preserving and reconstructing coastal marshes can help
         reduce storm damage.  Coastal wedands serve as storm surge
         protectors when hurricanes or tropical storms come ashore,  in
         the Gulf coast area, barrier islands, shoals, marshes, forested
         wedands and odier features of the coastal landscape can provide
         a significant and potentially sustainable buffer from wind wave
         action and storm surge generated by tropical storms and hurri-
         canes. (Source: Working Group for Post-Hurricane Planning for
         the Louisiana Coast)
                                               ••.^ NO WETLANDS
              This diagram indicates that wetlands reduce peak
              stormwater flows.  (Source: Kusler 1983)
          More Wetlands Mean Less Flooding
          These examples illustrate how protecting and restoring wetlands
          can reduce the destructive potential of flooding.  Wedand
          restoration and preservation is an important component of a
          comprehensive flood protection strategy. EPA, working with
          other federal agency partners, is a resource for state and local
          decision-makers, providing tools and limited funding for devel-
          opment of state wetland programs. Preserving wedands, along
          with other flood control measures, can offer a degree of protec-
          tion against flooding that is often more effective and costs less
          than a system of traditional dikes and levees. If more communi-
          ties protect existing wedands and increase the quantity of wet-
          lands through restoration projects, we will be better protected
          against  the consequences of floods.

                                                                                              Office of Water
                                                                                                   May 2006
On the Internet:
 Charles River Natural Valley Storage Area  	www.nae.usace.arrny.mil/recreati/crn/crnhome.htm
 Federal Emergency Management Agency	www.fema.gov
 Friends of the Chicago River	www.chicagoriver.org
 National Park Service	www.nps.gov
 The Wetlands Initiative	www.wetlands-initiative.org
 U.S. Army Corps of Engineers	www.usace.army.mil
In Print:
 Floods, Floodplains and Folks. 1996. National Park Service. Rivers, Trails and Conservation Assistance Program.
 Flood Damage Reduction in the Upper Mississippi River Basin—An Ecological Alternative. 2004.  Donald L. Hey, et al.
 The Wetlands Initiative, Chicago, IL. Available at www.wetlands-initiative.org
 Jarrett, R.D., and J.E.Costa.  1984. Hydrology, geomorphology, and dam break modeling of the July 15, 1982 Lawn
 Lake Dam and Cascade Lake Dam Failures, Larimer County,  Colorado: U.S. Geological Survey Professional Paper 1369.
 Johnson, Rex R. 1997. The Vermillion River: Managing the Watershed to Reduce Flooding. Clay County Conservation
 District, Vermillion, SD.
                                    Additional Wetland Resources
     For additional information, visit the U.S. EPA's website (www.epa.gov/owow/wetlands/),  call the toll-free
                       Wetlands Helpline at  1-800-832-7828 or refer to the sources below.
On the Internet:
 "A New Framework for Planning the Future of Coastal Louisiana
 after the Hurricanes of 2005." January 26, 2006. Working Group
 for Post-Hurricane Planning for the Louisiana Coast	www.umces.edu/la-restore
 Association of State Floodplain Managers	www.floods.org
 Association of State Wetland Managers	www.aswm.org
 "Reinventing a Flood Control Strategy." 1994. Donald L. Hey and
 Nancy S. Philippi. The Wetlands Initiative, Chicago, IL	www.wetlands-initiative.org
 Society of Wetland Scientists	www.sws.org
 U.S. National Weather Service	www.nws.noaa.gov
 Wetlands Status and Trends	http://wetlandsfws.er.usgs.gov
In Print:
 Bradley, A.A., K.W. Potter, T. Price, P. J. Cooper, J. Steflfen and D. Francz. 1994. Dahl, T.E. 1990. "Wetland losses
 in the United States: 1780's to 1980s." Washington,  DC. U.S. Department of Interior.
 "Flood analysis in DuPage County using HSPF," Proceedings of the Transportation Research Board (TRB) Annual
 Meeting, Washington, DC.
 Protecting Floodplain Resources, a Guidebook for Communities. June 1996. The Federal Interagency Floodplain
 Management Task Force.
 Shabman, L. 1994.  "Responding to the 1993 Flood: The Restoration Option," Water Resources Update, University
 Council on Water Resources, 95, 26-30.
 U.S. National Weather Service, 1993, "Update on Midwestern floods, heat and drought in the East: Special
 Climate Summary," 93/2, Climate Analysis Center.