Impact of floodplain and Stage 0 stream restoration on flood attenuation and floodplain exchange during small frequent storms

摘要

River flooding impacts human life and infrastructure, yet provides habitat and ecosystemservices. Traditional flood control (e.g., levees, dams) reduces habitat andecosystem services, and exacerbates flooding elsewhere. Floodplain restoration (i.e.,bankfull floodplain reconnection and Stage 0) can also provide flood management, buthas not been sufficiently evaluated for small frequent storms. We used 1D unsteadyHydrologic Engineering Center's River Analysis System to simulate small storms in a5 km-long,second-ordergeneric stream from the Chesapeake Bay watershed, andvaried channel restored (starting at the upstream end), restoration location, restorationbank height (distinguishes bankfull from Stage 0 restoration), and floodplainwidth/Manning's n. Stream restoration decreased (attenuated) peak flow up to 37and increased floodplain exchange by up to 46. Floodplain width and channelrestored had the largest impact on flood attenuation. The incremental effects of newrestoration projects on flood attenuation were greatest when little prior restorationhad occurred. By contrast, incremental effects on floodplain exchange were greatestin the presence of substantial prior restoration, setting up a tradeoff. A similartradeoff was revealed between attenuation and exchange for project location, but notbank height or floodplain width. In particular, attenuation and exchange were alwaysgreater for Stage 0 than for bankfull floodplain restoration. Stage 0 thus may counteracthuman impacts such as urbanization.