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tsunami_evacuationplanning (FeatureServer)

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Service Description: The potential tsunami inundation areas were generated to assist cities and counties in identifying their tsunami hazard. It is intended for local jurisdictional, coastal evacuation planning uses only.

Service ItemId: c51a48d574e24f7eb6470bf68f1ae08a

Has Versioned Data: false

Max Record Count: 2000

Supported query Formats: JSON

Supports applyEdits with GlobalIds: False

Supports Shared Templates: False

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Description: This feature set represents potential tsunami inundation areas for the coastal areas of the San Francisco Bay Region. It is a combination of the original 2009 Tsunami Inundation Area data and 2021 updates for Alameda County, Contra Costa County, City and County of San Francisco, San Mateo County, and Santa Clara County. This data does not represent inundation from a single scenario event. It was created by combining inundation results for an ensemble of source events affecting a given region. For this reason, all of the inundation region in a particular area will not likely be inundated during a single tsunami event.

All potential tsunami inundation areas data have been compiled with best currently available scientific information at their time of creation. Tsunamis are rare events; due to a lack of known occurrences in the historical record, this data includes no information about the probability of any tsunami affecting any area within a specific period of time.

Initial, 2009 tsunami modeling was performed by the University of Southern California Tsunami Research Center funded through the California Emergency Management Agency by the National Tsunami Hazard Mitigation Program. The tsunami modeling process utilized the MOST (Method of Splitting Tsunamis) computational program (Version 0), which allows for wave evolution over a variable bathymetry and topography used for the inundation mapping (Titov and Gonzalez, 1997; Titov and Synolakis, 1998). The bathymetric/topographic data that were used in the tsunami models consist of a series of nested grids. Near-shore grids with a 3 arc-second (75- to 90-meters) resolution or higher, were adjusted to "Mean High Water" sea-level conditions, representing a conservative sea level for the intended use of the tsunami modeling and mapping.

In order to enhance the result from the 75- to 90-meter inundation grid data, a method was developed utilizing higher-resolution digital topographic data (3- to 10-meters resolution) that better defines the location of the maximum inundation line (U.S. Geological Survey, 1993; Intermap, 2003; NOAA, 2004). The location of the enhanced inundation line was determined by using digital imagery and terrain data on a GIS platform with consideration given to historic inundation information (Lander, et al., 1993). This information was verified, where possible, by field work coordinated with local county personnel.

The 2021 update was produced collectively by tsunami modelers, geologic hazard mapping scientists, and emergency planning specialists from the California Geological Survey, the California Governor’s Office of Emergency Services, the Tsunami Research Center at the University of Southern California, and AECOM Technical Services. The Tsunami Hazard areas are developed for all populated areas at risk to tsunamis in California and represent a combination of the maximum considered tsunamis for each area. Local agencies, organizations, and other stakeholders assisted the State in the development of the hazard area as they will be used for evacuation planning at the community level.

The new modeling results use 10-meter resolution data and are part of a probabilistic tsunami hazard analysis. 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 (ARP).

Please refer to the following websites for additional information on the construction and/or intended use of the Tsunami Hazard Area:

Source data was downloaded from https://www.conservation.ca.gov/cgs/tsunami/maps

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The Association of Bay Area Governments' Resilience Program makes this data available, along with other hazard data, in an effort to provide a one-stop-shop for local governments to access data for hazard/resilience planning. More information on the program and its work can be accessed from the Resilience Program information page.


Copyright Text: California Geological Survey, 2021

Spatial Reference: 4326 (4326)

Initial Extent:
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Units: esriDecimalDegrees

Child Resources:   Info

Supported Operations:   Query   ConvertFormat   Get Estimates   Create Replica