Multi-hazard Non-regulatory Risk Maps for Resilient Coastal Communities of Washington State in Pacific Northwest Region of the United States

Abstract:

Washington Department of Natural Resources – Division of Geology and Earth Resources (WADNR-DGER) partnered with FEMA through the FEMA Cooperating Technical Partners (CTP) program to assess annualized losses from flood and other hazards and prepare supportive risk related data for FEMA’s coastal RiskMAP projects. We used HAZUS-MH analysis to assess losses from earthquake, flood and other potential hazards such as landslide and tsunami in the project areas; on shorelines of the Pacific Ocean and Puget Sound of Washington Grays Harbor, Pacific, Skagit, Whatcom, Island, Mason, Clallam, Jefferson and San Juan counties. The FEMA’s Hazus-MH tool was applied to estimate losses and damages for each building due to floods and earthquakes. User-defined facilities (UDF) inventory data were prepared and used for individual building damage estimations and updating general building stocks. Flood depth grids were used to determine which properties are most impacted by flooding. For example, the HAZUS-MH (flood model) run based on the 1% annual chance event (or 100 year flood) for Grays Harbor County, resulted in a total of $161 million in losses to buildings including residential, commercial properties, and other building and occupancy types. A likely M9 megathrust Cascadia earthquake scenario USGS-ShakeMap was used for the HAZUS-MH earthquake model. For example, the HAZUS-MH (earthquake model) run based on the Cascadia M9 earthquake for Grays Harbor County, resulted in a total of $1.15 billion in losses to building inventory. We produced GIS-based overlay maps of properties exposed to tsunami, landslide, and liquefaction hazards within the communities. This multi-hazard approach is an essential component to produce non-regulatory maps for FEMA’s RiskMAP project, and they help further improve local and regional mitigation efforts and emergency response plans, and overall resiliency plan of the communities in and around the coastal communities in western Washington.