AUTOMATED AND MANUAL GIS BASED MAPPING TECHNIQUES APPLIED TO SHALLOW WATER SEAFLOOR MAPPING AND CLASSIFICATION UTILIZING THE RAPID AIRBORNE MULTIBEAM MAPPING SYSTEM

Nearshore marine settings are continually exposed to natural processes and anthropogenic influences with the potential to induce significant morphological and environmental changes. Surveying, mapping, and classifying coastal areas provide the public and scientific institutions with a valuable resource to understand a regions morphology, ecological distribution, physical processes, and possible impact of human development. Implementation of the lidar Rapid Airborne Multibeam Mapping System (RAMMS) produces shallow water digital elevation models (DEM) comparable in quality (~2 meter bin size) to high-resolution multibeam echosounders (MBES), suitable for detailed mapping and feature identification. RAMMS transforms the approach to coastal studies by utilizing equipment that is light and compact allowing for aircraft flexibility, relatively low operation costs, and improved access to remote locations. Over 7,400 square kilometers of RAMMS bathymetry collected over Turks and Caicos were interpreted and classified using various automated and manual GIS techniques, with superior efficiency and quality with respect to traditional manual mapping techniques. Initially, the bathymetry DEM is used to produce a variety of maps including hillshades of various azimuth and altitude angles, slope, roughness, curvature, and aspect. Automated and qualitative manual mapping was performed by: 1) reviewing all derivative maps for distinct seafloor morphology trends and patterns, 2) comparing and integrating the bathymetry with the seafloor intensity and aerial photographs, 3) extracting relative lows representative of depressions, channels, scour, etc., 4) extracting relative highs representative of ridges, sediment waves, coral mounds, etc., 5) reclassifying seafloor intensity, slope, roughness, and/or curvature to define widespread areas of coral, ripples, rock outcrop, etc., and 6) refine and finalize classification extents with manual mapping. The results indicate that this regional nearshore mapping and classification methodology applied to the Turks and Caicos data can produce refined geodetic information and coastal characterization applicable to nautical charting, marine and coastal engineering, coastal zone management, and shallow water energy development.