The first phase of map and geospatial data publications, comprising six USGS Scientific Investigations Maps and associated data files centered on the Santa Barbara Channel, is now complete.
California Seafloor Mapping Program Reaches Milestone
The California Seafloor Mapping Program (CSMP) has released its latest set of maps and data, “California State Waters Map Series—Offshore of Refugio Beach, California,” U.S. Geological Survey (USGS) Scientific Investigations Map 3319. The “Offshore of Refugio Beach” maps lie within the western Santa Barbara Channel in southern California, and their publication marks a CSMP milestone: the first phase of map and geospatial data publications, comprising six USGS Scientific Investigations Maps and associated data files centered on the Santa Barbara Channel, is now complete. The maps are part of an ambitious collaborative effort to develop comprehensive bathymetric (seafloor depth), habitat, and geologic maps for all of California’s State Waters, which extend from the shoreline to 5.56 kilometers (3 nautical miles) offshore. These State Waters maps provide many types of information with a large range of applications. Examples include baselines for monitoring long-term change (from such factors as climate change and sea-level rise), geologic-framework data useful for assessing local earthquake and tsunami hazards, sediment distribution and thickness data that can serve as input to regional sediment management and sediment-transport modeling, physical and biologic habitat data that can provide a basis for ecosystem-based management, and data layers for use in decision-support tools for ocean planning.
CSMP began in November 2007, when the California Ocean Protection Council (COPC) allocated $15M for high-resolution bathymetric mapping, largely to support the California Marine Life Protection Act Initiative. Subsequent support from the COPC, the National Oceanic and Atmospheric Administration (NOAA), the USGS Coastal and Marine Geology Program, and many other partners has led to development of one of the world’s largest and most comprehensive seafloor-mapping datasets. More background information on CSMP is available on the California Seafloor Mapping Program website.
Development of map products, an effort led by the USGS Pacific Coastal and Marine Science Center (PCMSC), has been a CSMP focus. Each map set contains 10 downloadable pdf map sheets (most at 1:24,000 scale), an explanatory pamphlet, and digital geospatial data for a selected coastal “block.” Map sheets and (or) data layers show bathymetry, backscatter (strength of sound energy reflected from the seafloor during sonar mapping, which reveals information about seafloor roughness and composition), perspective views, seafloor “character” (video-supervised automated classification of bathymetry and backscatter data into such categories as “fine- to medium-grained smooth sediment” or “rugged anthropogenic material”), ground-truth imagery (photographs and video footage collected to verify interpretations of the bathymetry and backscatter data), potential habitats, seismic-reflection profiles (cross-sectional views of sediment layers beneath the seafloor), seafloor sediment distribution and thickness, and onshore-offshore geology (distribution of rock and sediment types, faults, and folds). Some map sets include additional thematic sheets that highlight detailed geomorphology (shape of the seafloor), predicted distribution of benthic macro-invertebrates (animals living in seafloor sediment), and natural offshore hydrocarbon seepage. Each map set represents a large collaborative effort (for example, the 67 maps and data layers in the six Santa Barbara Channel map sets have 31 co-authors) representing federal, state, academic, and private-sector partners.
The Santa Barbara Channel area extends from the steep Santa Ynez Mountains on the north to the Channel Islands and adjacent continental shelf on the south, and from Point Conception east to the Hueneme submarine canyon (see map at top). This dynamic landscape, characterized by diverse ecosystems and both urban and rural populations, faces increasing environmental stress due to development, climate change, and natural hazards. The map publications provide essential information for coastal management while enabling coastal research and modeling. Highlights include:
- Development of new methods and protocols for seamless onshore-offshore geologic mapping, and new strategies for geologic and geomorphic mapping of submarine canyons.
- Detailed mapping of the Ventura-Pitas Point Fault, Red Mountain Fault, Rincon Creek Fault, and other active faults and folds from the onshore into the offshore, providing important constraints on earthquake-hazard assessments.
- Maps that demonstrate the dramatic control of active faults on latest Pleistocene to Holocene sediment distribution and thickness.
- Mapping of more than 60 potential habitats, revealing significant amounts of soft sediment and isolated areas of rocky habitat that support nearshore kelp-forest communities and deeper rocky reefs. These habitats can be quantified and modeled for ecosystem characterization.
- Maps showing where common benthic macro-organisms—such as cup corals—are expected to occur based on real-time observations made by biologists watching video monitors during ground-truth surveys.
- Observation of bedrock overlain by very thin sediment cover in many areas in water depths of active sediment transport. As the coast changes and evolves, these areas could be buried more deeply or exhumed to form new rocky habitat.
- Recognition of submerged wave-cut platforms, keys to interpreting latest Pleistocene sea-level history.
- Documentation of widespread hydrocarbon-seep-induced topography on the Santa Barbara shelf; the largest concentration of pockmarks occurs near the head of the large Goleta landslide.
- Waves at Rincon, the world-famous surf spot, refract perfectly around a boulder delta that was deposited during a low stand of sea level and extends 1,500 meters offshore of Rincon Point.
And much, much more.
The Santa Barbara Channel map sets are available at the California State Waters Map Series:
- Hueneme Canyon and vicinity
- Offshore of Ventura, California
- Offshore of Carpinteria, California
- Offshore of Santa Barbara, California
- Offshore of Coal Oil Point, California
- Offshore of Refugio Beach, California
Three additional map sets for areas in central California are also available:
- Offshore of Pacifica, California
- Offshore of Half Moon Bay, California
- Offshore of San Gregorio, California