UNDERSTANDING COASTAL AND GLACIAL PROCESSES THROUGH MULTI-SCALE, MULTI-SENSOR DATA VISUALIZATION: DISCOVERY, HYPOTHESIS DEVELOPMENT AND TESTING

The nearshore environment is spatially and temporally dynamic and visualizing change through four dimensions can provide information on physical processes not otherwise attainable. Using myriad remote sensing data and spatial analysis techniques to elucidate shallow water, coastal settings and processes enhances the quality of scientific investigation.

Phase-measuring sidescan sonar has been used to collect swath bathymetry and acoustic backscatter imagery to demonstrate the effects of coastal engineering structures, document sediment transport pathways and map benthic habitats. Seismic reflection profiles and ground penetrating radar have been used to develop onshore/offshore stratigraphic profiles. Historical H-sheets have been used develop 3D surfaces for comparison with bathymetric lidar and recent swath bathymetry.

Swath bathymetry adjacent to a revetment that is being undermined by tidal currents shows flood-dominant channels immediately adjacent to ebb-dominant channels. This can be seen via bedform orientation. No bedforms are visible in the bathymetric lidar (1m grid cell) in this area. The acoustic backscatter imagery also documents a failing revetment, with slumps and individual blocks on the seafloor. This is not apparent in either bathymetric dataset. An anomalous feature seen in the acoustic backscatter imagery in 10 m of water along the open-ocean shoreline was later shown to be an outcrop of glacial lakefloor after seismic reflection profiles were collected over the feature and analyzed. A conical mound with 15 m of relief in 45 m of water was seen offshore of a shallow, shore-normal, trough-like feature with 1 m of negative relief over an alongshore distance of ~700 m. One initial hypothesis was of an active, evolving feature. Historical H-sheets from the mid- and late-19^th, and early 20^th century were digitized and the features were present, of similarly morphology and relief. A thorough understanding of the physical processes at work in a particular area can be greatly enhanced from multiple scales of data and a variety of instruments. Hypotheses developed with this in mind can be more easily and rigorously tested.