Foreshore Applications of X-band Radar

Abstract

The shallow waters of a nearshore region are dynamic and often hostile. Prediction in this region is usually difficult probably by our limited understanding of the physics or by availability of accurate field data. It is a challenge for traditional in situ instruments to provide these inputs with the appropriate temporal or spatial density at a reasonable cost. Remote sensing provides an attractive alternative. An X-band nautical radar system was employed for this study to examine alongshore propagation of low frequency run-up motion around the research pier HORS in Hasaki beach, Japan. Analyses on radar echo images were done to estimate longshore distribution of shoreline positions and inter-tidal foreshore profile using time-averaged images. Spatio-temporal variation of water fronts were digitized manually from cross-shore time-stack images. Run-up heights were then estimated from the digitized water fronts with the help of foreshore slope. Run-up variations under dissipative condition were parameterized with surf similarity parameter. Low frequency variances in the run-up motion were observed, which were traveling in the longshore direction. Longshore structures of this motion were examined and compared with different wave incidences during two typhoon events in the Pacific Ocean. Estimates of morpho-dynamic parameters during passage of different storms were analyzed and are explained in this chapter to demonstrate the potential of radar measurement in capturing essential characteristics of foreshore dynamics.