Modelling the effects of a changing storm climate on characteristics of inner shelf sand ridges

Abstract

A morphodynamical model is used to get further insight in the formation and long time evolution of the large scale bedforms on the inner shelf (circled at the front page). These sand ridges are formed on storm-dominated inner shelves over centeries and weaken the erosion of beaches. Their crest are shifted upstream with respect to where they are attached to the shoreface. Previous studies report constant stormy conditions over the entire formation time. The effects of changing storm climate are studied in this paper. Two changes in storm climate will be investigated: a sudden turn in wind and wave direction and a periodic change of 500 years in wind stress magnitude and offshore wave height. Modelling shows an increase in saturation height after a sudden turn, this is because of the Coriolis term in the shallow water equation. The saturation time after a sudden change is much shorter then when started with random bottom perturbation. Modelling with periodic stormy conditions results in a periodic migration speed and growth of the ridges. The time-averaged height of the ridge is also decreased because of the periodic conditons.