2. Natural and Beneficial Functions of Floodplains

The Great Mississippi Flood of 1927. Image courtesy of the National Archives and Records Administration.

Management of flood-prone areas for too long has been development-centered. For more than a century, the American society has sought to conquer cycles of flooding through engineered structural controls (Barnett, 2015). From the 1920s era Mississippi River levees that towered 40 feet in the air, to the current systems of stormwater infrastructure which have buried miles of natural drainage ways, flood control structures have made lands that were previously unfit for development available for development of agricultural fields and cities (Barnett, 2015). This strategy, to confine a waterway or waterbody to a predefined size and capacity so as to maximize the extent of developable land and keep flood water away from people and their property, has had dire consequences when those flood control structures fail. Furthermore, it has prevented floodplains from functioning naturally. Floodplains provide essential ecosystems services that have beneficial physical, biological, economic, and societal impacts.

From a physical perspective, floodplains (Wright, 2007):

  • Store and convey floodwaters
  • Filter nutrients and pollutants out of runoff
  • Reduce flood velocities
  • Reduce flood peaks
  • Moderate water temperature
  • Reduce the amount of sediment entering into surface waters
  • Enhance the quality of surface waters
  • Promote infiltration, groundwater and aquifer recharge
  • Reduce frequency and duration of low surface flows
  • Maintain sediment budgets

From a biological perspective, floodplains (Wright, 2007):

  • Enhance biological productivity
  • Enhance biodiversity
  • Are critical nursery habitat for fishes
  • Create and enhance waterfowl habitat
  • Are habitats for rare, threatened, and endangered species

From a societal perspective, floodplains (Wright, 2007):

  • Are sources of wild and cultivated plants
  • Enhance agricultural lands
  • Provide sites for aquaculture
  • Restore and enhance forest lands
  • Provide recreational opportunities
  • Are aesthetic resources
  • Are areas for scientific study and outdoor education
  • Contain cultural resources (historic and archaeological sites)

Wetlands are our nation's most productive ecosystems and while wetlands and floodplains are not synonymous, wetlands are the most prominent and familiar floodplain resources (Wright, 2007).  Although wetlands represent only a portion of overall floodplain acreage, essentially all coastal wetlands and most inland wetlands occur within floodplains (Wright, 2007). As a result, functions ascribed to wetlands can be considered, for most practical purposes, to be floodplain functions as well (Wright, 2007).

Wetlands on Captree Island, Long Island, New York. Jeanethe Falvey, US EPA via the Flickr Creative Commons.

Over the past 30 years, communities have increasingly realized the value of natural floodplain functions.  There has been a dramatic increase in restoration projects to daylight streams and restore confined channels to natural channels; there has been wider use of stream and river buffers to take advantage of the filtration capability of these areas to improve water quality; and there has been an increased recognition of stream and river fronts as recreational amenities and now design principles are being used to recreate these natural and beneficial functions through green infrastructure. All of these approaches harness the power of nature to maximize natural floodplain functions, decrease physical losses in floodplains, and increase community resiliency.

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