Coral reef degradation would significantly rise U.S. coastal flooding hazards

The degradation of coastal habitats, particularly coral reefs, increases the exposure of coastal communities to flooding hazards. However, this is an unrecognized and rarely quantified driver of risk. The protective services of ecosystems are not yet assessed in rigorous, risk-based, economic terms, and therefore, not considered in decision-making. Here we develop an integrated approach that combines state of the art hydrodynamic modeling with geospatial, social, and economic tools to assess flood risk along coral reefs populated areas of the entire USA and Trusted Territories. The study considers key factors usually ignored for flood modeling in other regions and ecosystems, but critical for reefs. We also assess how these coastal protection benefits may change in the future if reef degradation continues. For this, we map wave- and surge-driven flood zones at 10 m2 resolution along 3,100 km of US reef-lined shorelines for different storm probabilities. We quantify the increase in flood risk from reef degradation using the latest information from the U.S. Census Bureau, U.S. Federal Emergency Management Agency, and U.S. Bureau of Economic Analysis for different storm probabilities. Based on these results, the loss of protection from reefs would significantly increase flood hazard zones and subsequently risk. For example, over 71,500 people today fall in the 1-in-50-year flood zone in reef-lined coasts of the USA, but reef degradation would put at risk 47,300 more people (66% increase); 84.8 km2 of coastal land; and doubled economic damages to buildings ($4.5 billion); with an associated economic disruption that would increase from $4.4b to $6.8 billion. These data provide stakeholders and decision-makers with a spatially explicit, rigorous valuation of how, where, and under what storm conditions U.S. coral reef degradation will reduce critical flood reduction benefits. The results are built up from local-scale flooding that can be spatially aggregated to provide actionable information at all management-level scales (block level to state and national level). The approach provides management-relevant outputs to address an important gap in coastal management and risk preparedness. The overall goal is to ultimately reduce the risk to, and the resiliency of, U.S. communities from coastal flooding hazards.