Protecting the built environment in a barrier beach and marsh system: A case study of the Hampton-Seabrook Estuary, New Hampshire

Abstract

Many barrier beaches in the U.S. are areas of high socioeconomic activity that some stakeholders want to maintain despite being increasingly vulnerable to tidal and storm surge coastal flooding due to climate change and associated sea level rise (SLR). Here we examine how this can be accomplished using a hybrid of nature-based solutions and grey infrastructure under present and short-term future climates. Our case study site of the Hampton-Seabrook Estuary in New Hampshire has a barrier beach that is densely developed with residential, tourist, and commercial facilities and buildings; it is a major economic engine for the state. It also has extensive back-barrier tidal wetlands. Given the few options available for flood protection with present land uses, it was found that at least in the short term primarily gray approaches would have to be used to maintain the socioeconomic activities of this barrier beach system, such as elevating key roads and fortifying (but greening) existing seawalls. In some locations, however, dune maintenance programs could be expanded, and in other locations living shorelines could be constructed to increase resilience to storm flooding. In addition, many assets would have to rely upon purely site-specific protection measures such as elevating and flood proofing. Socioeconomically vulnerable residents would be afforded some benefits due to the built environment and anchor institutions being protected, but the costs of flood-proofing individual homes (or choosing to relocate) would likely be borne by individual homeowners. Adding public greenspace and walkable areas may afford the greatest health benefits to people in lower socioeconomic groups who typically have the least access. The reduction in flood risk can be accomplished with minimal environmental impacts compared to those the region will face from SLR alone. In the longer term, more consideration may need to be given to the concept of managed retreat. Unfortunately, the environmental benefits of retreat would not be recognized if short-term gray actions were successfully implemented.