USING VESSEL-BASED ACOUSTIC AND UNOCCUPIED AERIAL SURVEYS TO CREATE SEAMLESS ONSHORE/OFFSHORE MAPS: QUANTIFYING COASTAL CHANGE AND ASSOCIATED UNCERTAINTIES

The need for seamless maps in the coastal zone is critical and the resulting datasets have numerous applications. The value of these maps is to be found in treating the marine and terrestrial environments as two parts of one system. Too often marine surveys and terrestrial surveys are conducted separately without the design or intent to produce a single product using the two datasets that can provide a whole greater than the sum of its parts. Both of these mapping systems, Unoccupied Aerial Systems (UAS) and acoustic instruments have established uncertainties, but combining multi-modal datasets can introduce other uncertainties. The total area mapped via UAS surveys and acoustic surveys was 2.8 and 2.2 km², respectively. Approximately 0.28 km² from both surveys overlapped in the intertidal zone. Somewhat counterintuitively, the acoustic data better represented the bottom along most of that area. It was shown that while the UAS could map areas faster and at greater resolutions, intertidal flats with standing water, or poorly drained sediment, made the UAS data of poorer quality than the acoustic data. Results comparing the two datasets, methods, techniques, levels of effort and cost will be discussed as well as examples of geomorphological change that approaches and in some cases is within the range of uncertainty yet can still provide useful information with regards to ongoing coastal processes.