Nearshore Monitoring with X-Band Radar: Maximising Utility in Dynamic and Complex Environments

Authors: Atkinson, J., Esteves, L., Williams, J., Bell, P. and McCann, D.

Journal: Earth and Space Science Open Archive

DOI: 10.1002/essoar.10504567.1

Data quantifying the nature and range of bathymetric changes in the near-shore are required for coastal management and engineering works. However, due to high costs and complex logistics, bathymetric surveys are usually infrequent. This study demonstrates that ground-based X-band radar offers a cost-effective alternative to monitor seabed changes at relatively high frequency and over large near-shore areas. Through a robust data processing and quality control framework developed to validate radar-derived data and quantify uncertainties, bathymetric maps were obtained using an 18-month radar installation at Thorpeness, U.K. The analysis incorporates calibration of water levels and wave heights; validation of radar-derived water depth using concurrent multibeam surveys; the application of a method to reduce the influence of data scatter and outliers; and assessment of spatio-temporal variability of data quality due to varying wave heights and direction. For conditions when the wave height is >1 m, and the angle of wave approach relative to the radar is relatively small, the accuracy of the radar-derived depths is shown to be {plus minus}0.5 m at 40x40 m spatial resolution. At Thorpeness, quantification of changes exceeding this error was possible at time-scales as short as three weeks, and near-shore volume changes are seen to be of a comparable magnitude to historical longshore transport rates in the area. The use of radar can provide to coastal managers an early warning of changes in offshore bathymetry likely to impact vulnerable coastal locations; thereby allowing mobilisation of resources that may be required to protect lives and property.

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