Estimating Changes in Peak Flow and Associated Reductions in Flooding Resulting from Implementing Natural Infrastructure in the Neuse River Basin, North Carolina, USA

Abstract

As the frequency of more intense storms increases and concerns grow regarding the use of dams and levees, the focus has shifted to natural infrastructure (NI) for flood mitigation. NI has shown some success at small scales; however, little work has been carried out at the large watershed scale during extreme events. Three NI measures (afforestation, water farming, and flood control wetlands) were evaluated in the Neuse River Basin of eastern North Carolina. Detailed geospatial opportunity and hydrologic modeling of the measures were conducted in three subwatersheds of the basin and results were extrapolated to other subwatersheds. NI opportunity was greater and associated modeled peak flow reductions were larger for two subwatersheds located in the lower portion of the basin, where there is less development and flatter land slopes. Peak flow reductions varied spatially depending on the type and placement of NI combined with the hydraulic and morphologic characteristics of the stream network. Extrapolation of reductions to other subwatersheds produced a 4.4% reduction in peak flow for the 100 year storm at the outlet of the river basin in Kinston as a result of water farming on 1.1%, wetlands controlling runoff from 5.7%, and afforestation of 8.4% of the river basin.