SURVEY DESIGN ANALYSIS FOR THREE-DIMENSIONAL MAPPING OF BEACH AND NEARSHORE MORPHOLOGY

Abstract: Accurate documentation of beach and nearshore morphology is an essential component of coastal research and management. The Beach Erosion Research and Monitoring (BERM) program has been addressing this need through field intensive surveys for over a decade. Throughout this period BERM survey methods have evolved from conventional rod-level and sled-based profilers to our current acquisition method that couples Real-Time Kinematic GPS with shallow-water sonar. The introduction of these instruments has not only allowed for rapid and accurate collection of cross-shore profiles, but enabled acquisition of detailed alongshore data in a spatial context that was previously unachievable. Although the availability of this technology provides a more efficient means to measure the beach and nearshore, it remains vital to use the most appropriate survey design, one which will provide the most reliable and useful data for analysis. To determine the amount of data required to accurately represent beach and nearshore morphology in three dimensions, we designed an experiment within a 1400 m by 600 m survey area where we collected both shore-normal and shore-parallel data from the dune to a water depth of 8 m. Data specific interpolation algorithms, with strong anisotropy and optimal gridding parameters were applied to the data and the topographic output was systematically analyzed. Preliminary results indicate that utilizing only shore-normal data leads to interpolation artifacts, volume inaccuracies and only partially represents the true morphology. Analyses that make use of both shore-parallel and shore-normal data significantly reduce artifacts and provide more accurate representations of morphology and volume change