A benefit–cost analysis of floodplain land acquisition for US flood damage reduction

Flooding is the costliest form of natural disaster and impacts are expected to increase, in part, due to exposure of new development to flooding. However, these costs could be reduced through the acquisition and conservation of natural land in floodplains. Here we quantify the benefits and costs of reducing future flood damages in the United States by avoiding development in floodplains. We find that by 2070, cumulative avoided future flood damages exceed the costs of land acquisition for more than one-third of the unprotected natural lands in the 100-yr floodplain (areas with a 1% chance of flooding annually). Large areas have an even higher benefit–cost ratio: for 54,433 km 2 of floodplain, avoided damages exceed land acquisition costs by a factor of at least five to one. Strategic conservation of floodplains would avoid unnecessarily increasing the economic and human costs of flooding while simultaneously providing multiple ecosystem services. Flooding is the costliest natural disaster. Focusing on the United States, this analysis finds that by 2070 avoided damages exceed land acquisition costs for more than one-third of unprotected natural lands in the 100-year floodplain.