Roadway flooding as a bellwether for household retreat in rural, coastal regions vulnerable to sea-level rise

Sea-level rise (SLR) and coastal flooding in low-lying rural coastal areas will significantly impact residents' daily lives. The need to understand who may be affected and when is widely acknowledged in order to enable inclusive and cost-effective adaptation planning. Presently, planning resources generally focus on housing impacts; when will a house or neighborhood be inundated and which adaptation strategies are useful to improve the homeowner's fate? Housing, though, is but one of many types of reliable infrastructure needed to enable habitation at a parcel. Reliable roadways are another. In this study, we evaluate parcel-level impacts of SLR on local residents' ability to access key local amenities such as emergency services and grocery stores. More specifically, we focus on the impact of probabilistic SLR inundation scenarios on road infrastructure, and availability of alternative routes to meet the needs of residents. We find that in some instances, accessibility loss may come years before parcel inundation and could portend an earlier need for retreat than initially expected. We use Dorchester County, Maryland, U.S. as a case study. The county is extremely low-lying and is currently the second largest in the state by acreage, though its land area is expected to shrink in half by the turn of the century due to SLR. The results from the case study indicate that some parcels are not expected to be inundated by SLR but are expected to experience accessibility impacts. Limited access appears to be a bellwether for future household inundation and the forewarning stemming from accessibility loss can be significant in some locations. This work also shows the need for consensus surrounding which future scenario is planned for. While the results presented here are fairly insensitive to the degree of global carbon abatement, they are sensitive to exceedance probabilities.