Strategic land acquisition for efficient and equitable flood risk reduction in the United States

Land acquisition and subsequent prevention of future development in flood-prone areas offers high economic potential in reducing flood damage. However, there is an urgent need to evaluate the social outcome of this flood adaptation policy given the unequal exposure of vulnerable populations to flood impacts. Here, we use two additional evaluation criteria – equity of benefit distribution and population exposure reduction, along with economic benefit, to assess the social and economic outcomes of five land acquisition strategies in the United States. Under an assumed budget of US$1 billion, we found that land acquisition would generate an economic benefit of US$6.06 to $10.56 billion, ensure an equitable distribution of benefit, and remove 266,000 to 593,000 people from future flood risks. Compared to acquiring lands with high benefit-cost ratios, strategically acquiring lands in poorer and more populous areas would improve both social outcomes with only low to moderate reductions (13 %–43 %) in the economic efficiency. As global flood risk is projected to rise with disproportionate impact on the poor, our research highlights the social and economic capacities of strategic land acquisition for nationwide flood adaptation.