Estimation of design wave heights for coastal sea areas

Based on historical wind fields in the Bohai Sea, a sequence of annual extr emal wave heights is produced with numerical wave models for deep-water and shallow water. The design wave heights with different return periods for t he nearest deep-water point and for the shallow water point are estimated o n the basis of P-III type, Weibull distribution, and Gumbel distribution; a nd the corresponding values for the shallow water point are also estimated based on the HISWA model with the input of design wave heights for the near est deep-water point. Comparisons between design wave heights for the shall ow water point estimated on the basis of both distribution functions are HI SWA model show that the results from different distribution functions scatt er considerably, and influenced strongly by return periods; however, the re sults from the HISWA model are convergent, that is, the influence of the de sign wave heights estimated with different distribution functions for deep water is weakened, and the estimated values decrease for long return period s and increase for short return periods. Therefore, the numerical wave mode l gives a more stable result in shallow water design wave estimation becaus e of the consideration of the effect of physical processes which occur in s hallow water.