Seafloor character--Offshore of Santa Barbara, California

The seafloor-character map was produced using video-supervised maximum likelihood classification of the bathymetry and intensity of return from sonar systems. The classification was supervised using signatures defined by hand-drawn polygons located through sediment samples and video-observation ground truth surveying, applying methodology described in Cochrane (2008). The two variants used in this classification were backscatter intensity and derivative rugosity. Rugosity measures terrain ruggedness as the variation in three-dimensional orientation of grid cells within a neighborhood. Vector analysis is used to calculate the dispersion of vectors normal (orthogonal) to grid cells within the specified neighborhood. This method effectively captures variability in slope and aspect into a single measure. Ruggedness values in the output raster map can range from 0 (no terrain variation) to 1 (complete terrain variation). The calculation was performed using the Terrain Ruggedness (VRM) tool (for details, see Sappington and others, 2007).
Classes I, II, and III were delineated using multivariate analysis. Class IV (rugged anthropogenic material) values are a subclass of seafloor Class III, and Class V (smooth, hard anthropogenic material) values are a subclass of Class II; these pixels were depicted on the basis of visual characteristics and known location of man-made features. Class VI was assigned using a separate query describing a subclass of mobile sedimentary features (scour depressions), as defined by observations of megaripples (ripples that have wavelengths greater than 1 m) and moderate relief (Cacchione and others, 1984; Phillips, 2007). Class VI also includes areas that display some morphologic characteristics of scour depressions, but not all; some of these areas may fall under the class of sorted bedforms (Murray and Theiler, 2004; Trembanis and Hume, 2011). The resulting map (gridded at 2 m) was cleaned by hand to remove data-collection artifacts (for example, trackline nadir). Editing was performed in Photoshop, with which individual pixels were selected and values adjusted to remove noise. Selection occurred without antialiasing, and the resulting grid was identical but for the edited pixels. The six seafloor classes mapped in this area were then colored to indicate which of the following California Marine Life Protection Act depth zones and slope classes they belong: Depth Zone 2 (intertidal to 30 m), Depth Zone 3 (30 to 100 m), and Slope Class 1, 0 degrees to 5 degrees (flat). Depth Zone 1 (intertidal), Depth Zones 4 and 5 (greater than 100 m), and Slope Classes 2 to 4, greater than 5 degrees (sloping to vertical) are not present in this map area.
Additional References Cited:
Cacchione, D.A., Drake, D.E., Grant, W.D., and Tate, G.B., 1984, Rippled scour depressions of the inner continental shelf off central California: Journal of Sedimentary Petrology, v. 54, p. 1,280–1,291.
Murray, B., and Thieler, E.R., 2004, A new hypothesis and exploratory model for the formation of largescale inner-shelf sediment sorting and “rippled scour depressions”: Continental Shelf Research, v. 24, no. 3, p. 295–315.
Phillips, E., 2007, Exploring rippled scour depressions offshore Huntington Beach, CA: Santa Cruz, University of California, M.S. thesis, 58 p.
Trembanis, A.C., and Hume, T.M., 2011, Sorted bedforms on the inner shelf off northeastern New Zealand—Spatiotemporal relationships and potential paleo-environmental implications: Geo-Marine Letters, v. 31, p. 203–214.

Added Distribution_Information section to metadata to facilitate data download.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata.

Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed.

Performed minor edits to the metadata to correct typos. No data were changed

Metadata was modified to bring up to current USGS PCMSC standards. USGS Thesaurus and keywords were added, information for accompanying Open-File Report added to Abstract and Cross Reference sections, Point of Contact and Metadata Contact information was updated, and Process Steps were refined. Information about the data available for download and different Network Resource Name links and details were given in the Standard Order Process section. Minor typos were corrected. No data information was changed. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata dates to determine which metadata file is most recent.