Minimizing Flood Risks and Habitat Impacts Due to Post-Flood Recovery Efforts

Floods can have severe impacts on the physical and biological integrity of streams.  Excessive erosion and sediment deposition impact habitat over large spatial scales in a short period of time.  Common methods of flood recovery such as channel excavation, bank armoring, and reconstruction of public infrastructure and private property further impact habitat leaving channels smooth, homogenous, and fixed in place.  The resulting channels are often confined and isolated from floodplains.The best way to avoid habitat impacts due to post-flood recovery efforts is to minimize damages and the need for channel management.  Floodplain protection and reconnection is one approach to minimizing the need for channel work where river channels have room to move in the landscape, and deposited sediment after large floods can be removed from the floodplain with minimal impact to aquatic habitat.  Conserving the meander belt area to provide space for the river to migrate will reduce flood risks.  Adequate space for the river to move often avoids vertical instability caused by channel confinement and the need for invasive flood recovery. Managing rivers toward a least erosive, vertically stable condition is feasible during flood recovery, because working at the larger scales of the corridor and reach can be accomplished quickly and at relatively low costs compared to traditional channelization methods to simultaneously attain objectives such as public safety, hazard mitigation, and fish and wildlife protection.  Restoration of channel and floodplain geometry to minimize unnatural down-cutting or sedimentation is beneficial to people and habitat in the long run - reducing channel management costs and creating a physical foundation for the processes that create and maintain river habitat. In the wake of Tropical Storm Irene, Vermont struggled to balance protecting infrastructure such as roadways with controlling impacts to rivers.  Several site case studies will be presented to illustrate the challenges faced during flood recovery and the impacts over a range of existing conditions.  In the aftermath of Irene, a geomorphic-based approach to flood recovery is emerging that is built upon: management activities guided by existing geomorphic assessment data; a river corridor conservation easement program; and floodplain protection efforts.  The post-flood period has been marked by a heightened societal awareness of river processes and the fallacy of rebuilding to the pre-flood conditions without recognizing remaining flood risks.