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Living rivers are not just a fluid element confined within a static landscape. Rather, rivers that function like rivers – instead of mere water delivery channels – are a dynamic force that inundate, shape and reshape their floodplains in a seasonal rhythm. Inundated floodplains support a host of critical functions such as spawning, nursery and foraging habitat for a variety of fish, amphibian, and bird species. Floods are only viewed as undesirable, destructive events when they conflict with human settlements and land uses that have encroached into the floodplains after rivers have been tamed by dams or levees. Ironically, these flood control projects often exacerbate flood risks by attracting urban or agricultural development to floodplain lands.
The hundreds of billions of dollars that have been spent on flood control projects might be effective at minimizing damage from frequent moderate flood events, but such projects are often overwhelmed by infrequent, large flood events. When these large events do occur, they can cause significant flood damage, particularly where urban development is allowed on the floodplain, such as the catastrophic damages resulting from Hurricane Katrina in 2005 or by the Mississippi River in 1993. Despite more than a century of levee and dam construction, large areas of California’s Central Valley including portions of Sacramento and Stockton and the entire mosaic of delta islands are still subject to severe flood risks.
Meanwhile, dams that capture peak flood flows and levees that prevent flood flows from inundating floodplain habitats have reduced the area and frequency of habitat conditions necessary to sustain large populations of a variety of species.
NHI is developing an action program to foster a new and enlightened approach to flood management that recognizes the ecological importance of natural flooding and advances land use practices that will better protect lives and property from large flood events. We envision a future in which flood management systems will be built and operated to control only the infrequent, larger flood events while modifying floodplain land uses and constructing flood bypasses and corridors to accommodate the more frequent but modest flood events. NHI also advocates reoperating dams to mimic more natural flow regimes including moderate annual or biannual flooding to safely create inundated floodplain habitat in designated areas.
Restoration of designated floodplains not only restores habitat and reduces flood hazard risks, it also reduces conflicts between water supply, hydropower, and flood control objectives. Reservoir management for flood control requires maintaining low reservoir levels, which is at odds with maximizing water supply and hydropower benefits. This fundamental conflict over reservoir management will become exacerbated as climate change brings more extreme weather events.
As protection and creation of designated floodplains requires large-scale watershed planning, NHI is working to limit urban development in floodplains. Floodplain development reduces future options for enlightened floodplain management. Highly localized development at just a single point can constrain operations and management of hundreds of miles of river. There are several tools for preventing urbanization of low-lying flood plains, but their effectiveness depends on site-specific conditions and local decision-making processes. A comprehensive set of strategies, regulations and incentives is needed to prevent local parties from circumventing regulatory obstacles to develop floodplains.
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