Estimating coastal flood damage costs to transit infrastructure under future sea level rise

Abstract Future sea level rise (SLR) and associated increases in the frequency and intensity of coastal flooding poses significant threats to coastal communities and transit systems. Yet current literature and practice lack methods for estimating flood damage costs to transit systems. Here, we construct an event-specific flood damage cost estimation framework for transit systems, simulating separately flood ingress into underground spaces. We apply this framework to the MBTA rail transit system in Boston, estimating damages under several coastal flood events with SLR and project expected annualized losses (EAL) through 2100 with uncertain SLR. We estimate EALs to the MBTA system have doubled since 2008 to $24.4 M/year and are expected to reach $58 M/year by 2030 under all SLR scenarios. Our results suggest that absent adaptation schemes, particularly at tunnel ingress locations, coastal flood risk will continue to accelerate, potentially resulting in permanent inundation of underground and low-lying sections of the transit system.