An integrated operational forecast system for coastal, fluvial, and pluvial flooding in the San Francisco Bay area

Accurate and timely flood and precipitation information is critical for making emergency-response decisions regarding public safety, infrastructure operations, and resource allocation. Accordingly, the California Department of Water Resources has funded the development of a state-of-the-art Advanced Quantitative Precipitation Information (AQPI) system to provide near-term precipitation and flooding forecasts using an integrated observation and modeling framework for the San Francisco Bay area. The main goals of this collaborative project are to detect and track storms, nowcast high-resolution precipitation with cutting-edge radar technology, and forecast watershed and coastal flooding up to 72 hours in advance. This regional project is primarily a collaboration between National Oceanic and Atmospheric Administration (NOAA), and United States Geological Survey (USGS), supported with other local partners. This presentation will focus on the most downstream model in the AQPI framework, which is based on the USGS’s Coastal Storm Modeling System (CoSMoS: www.usgs.gov/cosmos). CoSMoS is a physics-based numerical modeling system for assessing coastal hazards from the combined effects of tides, rivers, storm surge, and waves. In particular, the USGS is using the Delft3D-Flexible Mesh Suite, developed by Deltares, that enables 1D/2D coupling and efficient and reliable modeling. As part of AQPI, CoSMoS incorporates the nowcast precipitation, winds, and pressure from the NOAA’s High-Resolution Rapid Refresh (HRRR) atmospheric model, as well as fluvial discharges from the NOAA’s watershed model (National Water Model). The coupled model forecasts the start, duration, and maximum water depth of flooding for areas in the zone of coastal influence within the nine counties that comprise the San Francisco Bay area. By integrating this complex set of models and incorporating the best possible observations to create operational forecasts, the AQPI system represents the next generation of forecasting frameworks and will provide demonstrable benefits in the face of hazardous flood conditions to communities across the bay.