Physical extreme sea level metrics may misrepresent future flood risk

Abstract:

Estimating changes in the frequency or height of extreme sea levels (ESLs; e.g., the 100-yr event) is a popular approach for illustrating future coastal flood risk to societies under various climate change scenarios. However, these metrics only account for physical water levels (i.e., the hazard). They do not consider societal outcomes (e.g., loss of life, property damage). As a result, physical ESL metrics and associated thresholds may give misleading estimates of future coastal flood risk. This has implications for climate adaptation decision-making and risk communication efforts that seek to quantify changes in coastal flood risk under different climate scenarios. Here, we illustrate how a risk measure using population exposure can lead to sizable differences in estimates of future coastal flood risk, relative to when only considering physical impacts. This suggests that physical ESL metrics may be poor surrogates for capturing some societal impacts. Considering a variety of human system, natural resource, and ecosystem-based outcomes may provide a more complete snapshot of coastal flood risk under different climate scenarios.