An Approach for Prioritizing Natural Infrastructure Practices to Mitigate Flood and Nitrate Risks in the Mississippi-Atchafalaya River Basin

Risks from flooding and poor water quality are evident at a range of spatial scales and climate change will exacerbate these risks in the future. Natural infrastructure (NI), consisting of structural or perennial vegetation, measures that provide multiple ecosystem benefits have the potential to reduce flood and water quality risks. In this study, we intersected watershed-scale risks to flooding and nitrate export in the Mississippi-Atchafalaya River Basin (MARB) of the central U.S. with potential locations of seven NI practices (row crop conversion, water, and sediment control basins, depressional wetlands, nitrate-removal wetlands, riparian buffers, and floodplain levees and row crop change) to prioritize where NI can be most effective for combined risk reduction at watershed scales. Spatial data from a variety of publicly-available databases were analyzed at a 10 m grid cell to locate NI practices using a geographic information system (GIS). NI practices were presented at the regional basin scale and local Iowa-Cedar watershed in eastern Iowa to show individual practice locations. A prioritization scheme was developed to show the optimal watersheds for deploying NI practices to minimize flooding and water quality risks in the MARB. Among the 84 HUC4 basins in the MARB, 28 are located in the Upper Mississippi and Ohio Rivers basins. The Wabash and Iowa-Cedar basins (HUCs 0512 and 0708, respectively) within these basins were found to rank among the uppermost quintile for nearly all practices evaluated, indicating widespread opportunities for NI implementation. Study results are a launching point from which to improve the connections between watershed scale risks and the potential use of NI practices to reduce these risks.