A numerical study of the effects of coastal geometry in the Bohai Sea on storm surges induced by cold-air outbreaks

Abstract

Strom surges are not only determined by the atmospheric forcing, but also influenced by the coastal geometry and bathymetry. The Bohai Sea, as one of China’s marginal seas, is seriously harmed by storm surges, especially those caused by cold-air outbreaks. As the coastline of the Bohai Sea has changed evidently these years, storm surges may have new characteristics due to the changes in the local geometry. This paper aims to find out these new characteristics by primarily investigating the influence of the changes in the local geometry on storm surges with numerical methods. 20 scenarios were constructed based on the track and intensity of the cold-air outbreaks to describe the actual situation. By analyzing the model results of the control scenarios, it is found that the main changes of the maximum surge elevation occur in the Bohai Bay and the Laizhou Bay. At the top of the Bohai Bay, the maximum surge elevation is obviously decreased, while in the Laizhou Bay, it is enhanced by the growing Yellow River Delta. This, however, does not suggest that the storm surges in the Laizhou Bay become more serious. A comparison of the risk assessment of storm surges in the Tanggu, Huanghua and Yangjiaogou regions shows that the risk of storm surges in these coastal areas is lightened by the evolvement of the coastal geometry. Particularly near Yangjiaogou, though the maximum surge elevation becomes higher to subject more areas to risk, the risk is still reduced by the evolvement of the Yellow River Delta.