Mapping shallow water coastal areas using a standard marine x-band radar

The bathymetry and currents in a 4km radius area of the Dee Estuary in Liverpool Bay have been mapped using a wave inversion of marine radar data without the need for any prior bathymetric data. The radar is mounted 30m above sea level on an island in the estuary and 10 minute sequences of radar images of the sea surface are recorded automatically each hour giving 360 degree coverage of the area. Several such records taken arond high tide during a moderate wave event have been processed to produce the map using a wave inversion that accounts for currents, frequency and amplitude dispersion. The results are compared to a combined LiDAR and Multibeam echosounder survey carried out in 2003, clearly identifying migrating sand banks within the estuary. The strength of this technique is in its ability to map large areas of bathymetrically complex shallow coastal waters rapidly, remotely and under storm conditions, with vertical accuracies generally better than +/-1m of survey data