Economic benefits of a rural distributed flood storage system

Abstract

Rural distributed storage systems are green infrastructure that decentrally store flood water across the landscape to reduce downstream flood peaks. Despite growing understanding of their flow reduction potential, the evidence base for their economic risk reduction is thin. This study quantifies the economic benefits of distributed storage constructed in an agricultural region of Iowa. The system was financed through the US National Disaster Resilience Competition, and adopted a voluntary conservation approach that provided cost-share assistance to landowners. Our sequential analysis employed high-resolution modeling of watershed hydrology, flood exposure of buildings and crops, and economic risk. Construction and maintenance costs were included in scenario analyses of constructed storage structures and maximum potential structure buildout. The maximum benefit-cost ratio was 0.34, falling below the traditional threshold of 1.0 used for project selection in hazard mitigation. The results are highly sensitive to the geospatial accuracy of exposed buildings, and the flood-reduction benefits diminished at larger spatial scales. To improve risk reduction benefits, project siting should consider the location along the stream network and proximity to high-value properties. The inclusion of nonmonetary co-benefits such as improved water quality, landowner amenities, ecosystem services, and community collaboration would also strengthen the case for resilience cost-effectiveness.