Mapping California’s Seafloor

UPDATE August 2012 – The first set of formal map products from the California Seafloor Mapping Program are now available on the United States Geological Survey website.  This first map set covers Hueneme Canyon and vicinity, and includes 12 map sheets displaying seafloor characteristics, an explanatory pamphlet, and a data catalog of GIS files.  More information on map product development is available on and on the USGS project page, which includes a spreadsheet that documents works accomplished.

The ocean is a vital part of life in California, intimately affecting the lives of all Californians. The oceans are drivers of weather systems and of climate; they are highways for marine commerce and a major reservoir of natural resources; they hold potential for energy development, and are a buffer for national security, yet we know more about the surface of the moon than we do about the seafloor.

It has only been in the past few years that technology has advanced to the point where we can accurately and efficiently determine the shape of the seafloor over large areas. The OPC has assembled a team of experts from state and federal agencies, academia, and private industry to develop the best approach to mapping and classifying estuarine and  marine geologic and benthic habitats, while at the same time updating all nautical charts. Initiated in 2007, the California Seafloor Mapping Project (CSMP) is collecting bathymetry (underwater topography) and backscatter data (providing insight into the geologic makeup of the seafloor) that will be turned into benthic habitat and geologic base maps for all of California’s state waters from the mean high water line out to 3 nautical miles. The CSMP will have many uses beyond its original goal of supporting the design and monitoring of marine reserves. Accurate statewide mapping of the seafloor will also:

  • Improve climate change and ocean circulation models
  • Help evaluate the potential for ocean energy
  • Improve our understanding of ecosystem dynamics
  • Identify submerged faults and improve our understanding of tsunami potential
  • Enable more effective regulation of offshore develpment
  • Improve maritime safety
  • Improve our understanding of sediment transport and sand delivery


This is an example of corrections to a nautical chart that are possible now that there is more detailed information about the seafloor. In blue are the original published depth soundings, some dating back to the 1800s. In red are the newly discovered depths. In partnership with NOAA, the CSMP will facilitate the updating of navigation charts with new digital, modern data. The resulting maps will provide better information on dangers to navigation.

When the CSMP began, less than a third of California’s submerged lands had been mapped in sufficient enough detail to distinguish benthic habitats and geologic features. Using a variety of state of the art mapping technologies including digital multibeam and sidescan sonar systems, the CSMP team is now collecting the remaining hydrographic data, groundtruthing the sonar data using video cameras, and translating the results into a suite of maps that will be provided to resource managers and the public in a variety of formats ranging from hardcopy paper maps to customizable digital maps served on the web. This data will also be combined with high resolution topographic LiDAR data along the entire California coastline. Once they are available, the complete onshore-offshore elevation maps will be critical to improving climate change modeling and mitigating the impacts of  sea level rise.

In order to truly improve ocean management in the face of a rapidly changing climate, it will be critical that we map changes in the composition of the seafloor over time. The baseline geologic and benthic habitat maps created through the CSMP will guide future research and help identify the more dynamic areas along the coast that will be vulnerable to sea level rise or storm surges, sediment transport and coastal erosion, or diminishing habitats for living marine resources. This data will continue to inform decision-makers and move us toward a more sustainable use of our ocean resources.

Creating high-resolution seafloor maps along the west coast was identified as a priority in the West Coast Governor’s Agreement in Ocean Health. OPC staff is working with colleagues in Oregon and Washington to create standards for mapping, share successes, and identify collaborative opportunities and regional priorities.

This project is designed to employ the latest technology that enables seamless integration of information across the shoreline to capture bathymetry in the ocean, as well as imagery and elevation across the terrestrial watershed. We believe that this project will set a new standard of mapping that will pave the way for better informed decision-making in this critical region.

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