On improving the bed stress formulation in storm surge models

A method of improving the representation of bottom stress in storm surge models (an “enhanced” bed stress model) is tested using a fine‐mesh model of the Celtic and Irish seas and is compared with results from a “conventional” two‐dimensional model. The approach uses a convolution method to determine the bed stress, rather than relating it directly to the depth mean current, as in a “conventional” storm surge model. For the region considered, comparisons of surge elevations computed with both models, and observations, show only a slight improvement of surge elevation in the near‐coastal region with the “enhanced” bed stress model. However spatial distributions of bed stresses from the two models do exhibit significant differences which are important in considering sediment movement paths during major storms. The magnitude and direction of the bed stress vectors computed from the “enhanced” bed stress model are in excellent agreement with calculations using a full three‐dimensional model of the area. This suggests that the “enhanced” bed stress model can compute a bed stress that is not significantly different from that in a full three‐dimensional model, at a fraction of the computational cost.