Creation of surficial substrate maps for multidisciplinary marine studies in San Francisco Bay

As part of a cooperative grant provided by NOAA’s National Ocean and National Marine Fisheries Services, approximately 120 km2 of San Francisco Bay were mapped using archived multibeam bathymetric data and another ~40.5 km2 were mapped using recently acquired side-scan sonar data during 2002-2003. These data were interpreted into potential habitat types and further evaluated for natural (normally) and human-induced disturbances. Ninety-one distinct potential habitats were identified, of which 74 were composed of soft, 12 of mixed, and 5 of hard substrates. Bay floor sediment samples were used to document substrate composition and document (“groundtruth”) habitat interpretations. Modern sedimentation, from fluvial input and tidal scouring and deposition, has resulted in a dynamic and complex Bay floor. Strong currents have produced large sediment wave and dune fields, rippled sediment patches, and scoured channel floors and walls. Soft habitats composed primarily of mud and/or sand dominate the region, whereas hard (rock) and mixed habitats are relatively rare and occur mainly in shallow areas adjacent to peninsulas and islands. Anthropogenic effects such as dredge material and debris-fields, borrow pits, dredged channels, and blasted bedrock knolls and normal disturbances such as sand waves are distinctly displayed in the data and comprise ~63.5 km2 of the total area mapped. With the increasing demand for construction aggregate and development in the greater San Francisco Bay area, and the need to maintain and expand dredged channels and lower bedrock knolls to allow the safe passage of deep-drafting vessels, many potential habitats will be impacted. The extent and effects of these impacts can be better evaluated as a result of this study. A manuscript resulting from this work is currently in press.

 

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