Floodplain restoration is the process of fully or partially restoring a river's floodplain to its original conditions before having been affected by the construction of levees (dikes) and the draining of wetlands and marshes.
The objectives of restoring floodplains include the reduction of the incidence of floods, the provision of habitats for aquatic species, the improvement of water quality and the increased recharge of groundwater.
Anthropogenic impacts on floodplain mostly target the lateral connectivity between rivers and their floodplains, so many restoration methods focus on removing human-made structures that disrupt connectivity.[1] One type of floodplain restoration are levee setbacks and dam removal, either full or partial, to allow for rivers to migrate within a space that is closer to the natural floodplain.[2] Another method is through a "beaded approach" with allows small portions of a floodplain to be restored to natural habitat and functions .[2] The removal of levees and/or weirs can allow for the reconnection of river channels to their floodplain.[2] Riverside embankments through the creation of overflow sills and creating artificial opening at inflow channels can help increase channel connectivity to the floodplain.[3] Restoring drained or degraded wetlands can help increase floodplain connectivity.[4]
Floodplain restoration can restore previously lost or degraded ecosystem services. These ecosystem services can be categorized by supporting, regulating, provisioning, and cultural services.[5] Restoring floodplains can help regulate flood events and mitigate flood related damage.[6] Floodplain restoration can also increase biodiversity by creating new or restoring degraded habitat and encourage growth of native species.[7][8] Methods of wetland restoration in the floodplain, can help better water quality.[9] Reconnecting rivers to their floodplains promotes carbon storage in soil and regulates processes within soil.[8]
There are several issues that may arise when planning and/or implementing floodplain restoration projects. Since floodplain restoration involves a wide range of partnerships and stakeholders, a lack of communication between parties and differences ideas or priorities for restoration goals can be a constraint for restoration projects.[10] There is also the potential for a higher value or desire placed into immediate flood-defense and current land-use practices rather than the ecological or environmental benefits, which can stall or prevent floodplain restoration.[10][11] It is also important to include the socio-economic aspects of floodplain restoration, so when this becomes a constraint to projects that do not consider these aspects. Restoration efforts need to be properly and continuously monitored to determine effectiveness and benefits.[1]
This is not an exhaustive list
One of the drivers for floodplain restoration is the EU Water Framework Directive. Early floodplain restoration schemes were undertaken in the mid-1990s in the Rheinvorland-Süd on the Upper Rhine, the Bourret on the Garonne, and as part of the Long Eau project in England.[16] Ongoing schemes in 2007 include Lenzen on the Elbe, La Basse on the Seine and the Parrett Catchment Project in England. On the Elbe River near Lenzen (Brandenburg), 420 hectares of floodplain were restored in order to prevent a recurrence of the Elbe floods of 2002. A total of 20 floodplain restoration projects on the Elbe River were envisaged after the 2002 floods, but only two have been implemented as of 2009 according to the environmental group de:BUND.[17]
Floodplain restoration in the United States is driven by The Clean Water Act (1972), The Endangered Species Act (1973), and various state level legislations.
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