Adapting to sea level rise and storms.

It is well known that sea level rise (SLR) will force retreat along rural coastlines but that cities will need to protect their coasts. But how exactly should seawalls, flood insurance, and retreat be used over time to minimize the overall cost of coastal flooding to society? This paper examines dynamic coastal adaptation in six cities along the eastern seaboard of the United States through 2180. We argue that seawalls should be designed to minimize the sum of seawall costs and expected residual flood damage. Flood insurance for residual damage can address risk aversion. The results reveal that only areas with high expected damage per kilometer of coastline require walls. Only a few segments of most cities need a wall now. The optimal wall height is about 1-2 m. SLR will force more urban seawalls to be built over the next 100 years. The faster SLR rises, the sooner they will need to be built.