There are 88 NPS park units designated as Ocean and Coastal Parks that encompass 11,000 shoreline miles and 2.5 million acres of ocean and Great Lakes waters. Due to the large and complex nature of these park units, managing natural and cultural resources can be difficult. Benthic (meaning ocean floor or lake bottom) habitat maps are a spatially explicit way to identify submerged features. They are created from a combination of remote sensing data types (light detection and ranging [lidar], sonar, imagery) and physical sampling (underwater video and soil samples). These maps are considerably valuable to resource managers, as baseline information is established to quantify and monitor aquatic species habitats, coastal processes, cultural resources, post-incident damage, and natural disturbances. Unlike terrestrial areas that have had decades of exploration and research, many underwater areas in these parks are unmapped and remain categorized as water. A gap analysis showed that only five parks have benthic habitat maps that cover the full spatial extent of the park. Fifteen parks have benthic habitat maps that cover approximately 50% of the submerged extent. Nearly all of the remaining parks have little to no benthic habitat information even though most, aside from Alaska, have adequate data coverage to begin the mapping process.
The Ocean and Coastal Resources Branch of the NPS has partnered with agencies and universities to update and complete benthic habitats maps for park units. The Great Lakes Region is the current mapping priority and NPS staff have collected multibeam sonar and backscatter data at all the Great Lakes Parks. Sonar boats cannot collect data shallower than -3 meters due to instrumentation; therefore, topobathymetric lidar (specialized lidar that penetrates shallow, clear water) is used to fill in nearshore areas and create a seamless bathymetric dataset. Multiple datasets were derived from the bathymetry (i.e. slope, rugosity) to inform general geomorphological features and potential habitat types. The backscatter data provide information about the relative hardness or roughness of the bottom (i.e. sand, rock).
The sonar derivatives and backscatter data were each segmented via object-based analyses to delineate potentially unique habitats and bottom surface types, respectively. The next phase will use bottom photos and videos to classify and validate the segmented areas. The Coastal and Marine Ecological Classification Standard (CMECS) will be applied to all park units for thematic consistency. The preliminary maps created in the Great Lakes have identified a number of sunken ships, interesting geological features, and baseline habitat information.
This effort extends mapping of Sleeping Bear Dunes National Lakeshore offshore into Good Harbor Bay, Michigan, and shows (a) depth in meters, (b) lake bottom geomorphological features, (c) backscatter atop a hillshade, and (d) habitat segmentation with 15 potentially unique classes.