Quantifying climate change risk through natural hazard losses to inform adaptation action

Climate change is expected to increase the frequency and severity of many natural hazards. In particular, coastal communities are often exposed to multiple hazards, exacerbated by climate change. We present a methodology to quantify the increase in multi-hazard risk due to climate change. The methodology includes a probabilistic description of independent hazard pathways, defined as sets of individual and cascading hazards that are statistically independent, run for multiple levels of climate change impact. We also quantify the risk reduction from adaptation actions. The approach integrates probabilistic hazard analysis and loss assessment. With this approach, we identify the hazards contributing most to risk under multiple amounts of climate change. This methodology is applied to a case study of residential housing in Alameda, California, USA, considering how sea level rise impacts multiple hazards: earthquakes, coastal flooding, and tsunamis. For the case study location, we identify that the highest annualized risk shifts from earthquakes to coastal flooding as sea levels rise. We assess how different adaptation actions would reduce the risk today and under sea level rise, highlighting the need to consider frequent and infrequent losses.