| A three-dimensional numerical prediction system for storm sedimentation has been constructed, which includes a cyclonic wind field, coastal circulation, storm waves, the combined effect of steady currents and waves on the benthic boundary layer, suspended and bed load transport of sediment, and conservation of mass at the sea floor.;Storm-driven circulation and event-bed genesis were studied with the model system, using four historical tropical cyclones which crossed the Texas-Louisiana continental shelf. These numerical experiments demonstrated the dominant physical processes operating during severe storms, and the dependence of storm bed variability on shelf geometry, sediment distribution, and storm track. The model predicts that finer sediment is transported landward to the right of the storm track, whereas sand is resuspended on the inner shelf, eroded from the shoreface, and transported seaward to the left of the track. Maximum predicted scour depths are less than 1 m, and event-bed thickness is on the order of 50 cm. For all cases sandy beds thicker than 5 cm were restricted to specific locations along the coast. When a mud line was introduced at the 20 m isobath, the bed comprised predominantly mud seaward and sand landward, with the greatest thickness occurring within muddy sediment.;The vertical current structure predicted by the geostrophic model did not develop. Instead, one-layer along-shelf flow was predicted because the thickness of the wind-mixed layer exceeded water depth over the shelf. Most of the continental shelf fell within the friction-dominated zone, in which the upper and lower boundary layers overlap. This suggests that the strong winds within the main storm region during severe storms turbulently mix the coastal sea, reducing density stratification and driving shore-parallel flows.;The model system needs an improved wind-field algorithm; more realistic density stratification; a better entrainment function for fine sediment; the swell component of the wind-wave field; and feedback between currents, waves, and the benthic boundary layer. Nevertheless, the sedimentation patterns predicted for these storms compare favorably with observations from modern shelves, suggesting that the dominant physical processes are being captured. |
