Hydrodynamical and morphological patterns of a sandy coast with a beach nourishment suffering from a storm surge

ABSTRACT The beach of Shanhai Pass in the eastern Qinhuangdao, China, which was nourished in August 2017, suffered from a storm surge induced by the tropical cyclone Ampil in July 2018. In order to investigate the storm surge hydrodynamical process and the morphological response of the beach to the storm, an outer wave-current coupled model based on Delft3D and an inner morphodynamical model based on Xbeach are applied and well-validated against the measurements. The model results show that the storm-induced current vector and the wave vector at the Shanhai Pass beach rotates clockwise corresponding with the wind vector during the storm. The storm surge is positive in the north of the Bohai Sea and negative in the south when the wind speed reaches the maximum. The wind-induced surge makes the dominant contribution to the total storm surge at the study area and the air-pressure-induced surge is the second factor for far away area from the surf zone, where the wave-induced surge is negligible. The storm impact regime is determined as swash regime, and the sand of the beach foreshore is transported offshore by the storm, however, the eroded sand is transported onshore by the mild waves during the recovery period.