State of California's Update to the Tsunami Inundation Maps for Evacuation Planning
Abstract
The California Geological Survey (CGS) and the California Governor's Office of Emergency Services (Cal OES) are in the process of generating the third generation of statewide tsunami inundation maps for evacuation planning. National Tsunami Hazard Mitigation Program (NTHMP) guidelines recommend re-evaluating the tsunami hazard every 5-10 years or when significant development in modeling capability or data quality are available. Over the past 10 years, significant advances in tsunami source characterization and computer modeling have been made. The second-generation State inundation maps, published in 2009, were modeled at a 30-to-90m resolution for various local and distant tsunami sources. New modeling results, commissioned by CGS and completed by AECOM, use 10-m resolution data and are part of a probabilistic tsunami hazard analysis (PTHA) covering all low-lying, populated areas of California's coastline. The tsunami sources selected for inclusion in development of the new maps represent large, realistic events primarily from the Alaska and Cascadia subduction zones, equivalent to a baseline of the 975-year average return period. Delineating the landward extent of inundation uses a conservative, hybrid approach of combining the 2009 local- and distant-source models with the new and improved model results. The extent was further augmented using high-resolution data and GIS tools available for tsunami inundation line enhancement. A set of rules were developed to better define the maximum inland inundation line including a method to remove artifacts such as islands and holes from the modeled data and to smooth the final inundation line. The final inundation map results were digitally reviewed, and modified areas were verified in the field by CGS, Cal OES, and local agencies. The updated State inundation maps will be used by local decision-makers as a basis to inform decisions regarding evacuation planning.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNH43D0973G
- Keywords:
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- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDS;
- 4333 Disaster risk analysis and assessment;
- NATURAL HAZARDS;
- 4341 Early warning systems;
- NATURAL HAZARDS;
- 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL