CMECS map for an area of the Oregon Outer Continental Shelf relevant to renewable energy
Authors: Cochrane G R , Hemery L G , Henkel S K , Schroeder D M 
Published: September 2017

In 2014 the USGS and the BOEM entered into an Intra-agency agreement to map an area of the Oregon Outer Continental Shelf (OCS) off of Coos Bay, Oregon under consideration for development of a floating wind energy farm. The BOEM requires seafloor mapping and site
characterization studies in order to evaluate the impact of seafloor and sub-seafloor conditions on the installation, operation, and structural integrity of proposed renewable energy projects, as well as to assess the potential effects of construction and operations on archaeological resources. The
mission of the USGS is to provide geologic, topographic, and hydrologic information that contributes to the wise management of the Nation's natural resources and that promotes the health, safety, and well-being of the people.
For the Oregon OCS study the USGS acquired multibeam echo sounder (MBES) and seafloor video data surrounding the proposed development site, a 95 km2 area 15 miles offshore of Coos Bay, Oregon. The USGS subsequently produced a bathymetry digital elevation model and backscatter intensity grids.
Analysis of the video data was conducted by OSU and a Coastal and Marine Ecosystems Classification Standard (CMECS) geoform and substrate component interpretation of the MBES data was conducted by the USGS.
Though combinations of mud and sand dominate the surficial substrate there is a diverse assortment of geomorphologic features related to geologic processes. Video supervised numerical analysis of the MBES backscatter intensity data and vector ruggedness derived from the MBES bathymetry data was used
to produce a substrate model for the study area called a seafloor character raster. The sea floor character raster consists of three substrate classes, soft-flat areas, hard-flat areas and hard-rugged areas that were used to generate CMECS substrate attributes. For substrate polygons that had video
grain size information a finer level of CMECS grain size was added to the map. CMECS geoform attributes were produced using depth, slope and benthic position index classes to delineate geoform boundaries. Seven geoforms were identified in this process including ridges, slump scars, slump deposits,
basins and pockmarks. There is one anticlinal ridge where bedrock is exposed, a slump and associated scarps, and pockmarks. Pockmarks are seen in the form of fields of small pockmarks (&amp;lt; 100 metres diameter), a lineation of large pockmarks with methanogenic carbonates, and areas of large
pockmarks that have merged into larger variously shaped depressions. The slump appears to have originated at the pockmark lineation. Existing multichannel seismic data was examined to attempt to identify crustal faults associated with pockmark areas and lineations. Faults related to anticlines could
be inferred by displacement of reflecting strata but structures related to pockmarks could not be resolved.
Statistical analysis of the video data for correlations between substrate, depth and biotic assemblages by OSU resulted in the identification of seven biomes, three hard bottom biomes and 4 soft bottom biomes. A biotope map was generated using the seafloor character raster and the substrate and
depth values of the biomes. Hard substrate biotopes were small in size and were located primarily on the ridge and in pockmarks along the pockmark lineation. The soft bottom biotopes consisted of large contiguous areas delimited by isobaths.