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Topobathymetric Model for the Southern Coast of California and the Channel Islands, 1930 to 2014

August 13, 2018

To support the modeling of storm-induced flooding, the USGS Coastal National Elevation Database (CoNED) Applications Project has created an integrated 1-meter topobathymetric digital elevation model (TBDEM) for the Southern California Coast and Channel Islands. The Channel Islands are a chain of eight islands where years of isolation has created unique fauna, flora, and archeological resources. The archipelago extends for 160 miles (257 km) between San Miguel Island in the north and San Clemente Island in the south. Five of the islands are part of Channel Islands National Park (Anacapa, Santa Cruz, Santa Rosa, San Miguel, and Santa Barbara), and the waters surrounding these islands make up the Channel Islands National Marine Sanctuary. High-resolution coastal elevation data is required to identify flood, storm, and sea-level rise inundation hazard zones and other earth science applications, such as the development of sediment transport and storm surge models. The new TBDEM consists of the best available multi-source topographic and bathymetric elevation data for Southern California including the Channel Islands onshore and offshore areas. The Southern California TBDEM integrates 49 different data sources including topographic and bathymetric LiDAR point clouds, Interferometric Synthetic Aperture Radar (IFSAR), hydrographic surveys, single-beam acoustic surveys, and multi-beam acoustic surveys obtained from USGS, NOAA, California State University - Monterey Bay, and Los Angeles County. The topographic and bathymetric surveys were sorted and prioritized based on survey date, accuracy, spatial distribution, and point density to develop a model based on the best available elevation data. Because bathymetric data are typically referenced to tidal datums (such as Mean High Water or Mean Low Water), all tidally-referenced heights were transformed into orthometric heights that are normally used for mapping elevation on land (based on the North American Vertical Datum of 1988). The spatial resolution is 1-meter with the general location ranging from the Mexican Border to Point Conception, and extending offshore to a depth of 2,847 meters. The overall temporal range of the input topography and bathymetry is 1930 to 2014. The topography surveys are from 2005-2014. The bathymetry surveys were acquired between 1930 and 2014. Some of the nearshore void zone (not covered by lidar or multibeam) was filled with NOS surveys from 1967 and 2013.