Abstract: High resolution bathymetric data along the Huadianhuiba sea dike, a typical eroding coast on the northern coastline of Hangzhou Bay, was collected to analyze seabed evolution. A wave model covering the Changjiang Estuary and Hangzhou Bay was built to obtain the wave elements along the sea dike. Then, sensitivity analyses were carried out to calculate the impacts of coastal erosion on the wave elements, the required crest elevation, and the intensity of the seaside dike revetment. The results indicate that under a design condition of a 200 year return period with increasing water depth in front of the sea dike, the mean wave height and wave period are almost stable, while the wave length and H₁% are significantly increased. The increased wave length, due to the topography deepening, is found to be a major factor for the subsequent wave run-up, which reduces the defense standard of sea dikes at crest elevation. In addition, the required intensity of the seaside dike revetment increases significantly with the depth of water in front of the sea dike. This indicates that a safety margin should be accounted for in design of the sea dike.

Key words: coastal erosion, safety of sea dike, wave elements, crest elevation, intensity of the seaside dike revetment