Sonoma Valley Flood Risk Assessment

Sonoma Water needed to understand the costs of existing flood risk as a starting point for evaluating mitigation projects. Using flood modeling from Environmental Science Associates, Radbridge assessed more than 4,000 structures across five flood event sizes. We estimated damage to buildings and contents, household displacement costs, lost time, and travel delays using methods consistent with FEMA guidance.

The preliminary analysis estimated average annual flood losses of $18.2 million, accounting for the likelihood and consequences of different flood events. Results for individual structures and study areas give Sonoma Water a baseline for estimating the losses proposed projects could avoid. The calculations can be updated as the agency develops mitigation alternatives and obtains more detailed information.