Two-dimensional numerical modeling of storm deposition on the northern California shelf

A two-dimensional, across-shelf sediment-transport model has been developed to simulate storm deposition on continental shelves. This paper describes the structure of the model and related algorithms. In the model, the time-dependent sediment resuspension, transportation and deposition, and across-shelf transport gradients are simulated as responses to storm waves on the Eel shelf, northern California. The simulations show that the pattern of storm deposition on the sandy inner shelf is different from that on the muddy middle and outer shelf. Storm-bed thickness decreases seaward across the inner-shelf sandy zone as far as the 50-m isobath. Farther seaward, storm-bed thickness increases as the mud component in the sea floor becomes abundant, then decreases again, as the weakening of bottom-wave motion with greater depth becomes the dominant control. Storm-bed thickness in the mud zone thus has a nearly symmetrical cross-shelf pattern, with the maximum thickness at a water depth of 70 m. The pattern suggests that while the sequence of new beds found in February 1995 on the Eel shelf may have had a flood source, their geometry reflects storm resuspension and transport. The new muds found in these beds may have been reworked, transported and redeposited several times by storm waves and other oceanic forces. Numerical simulations illustrate that the critical bottom shear stress for mud erosion, tau(e), and the coefficient for sand resuspension, gamma(0), are more important than other parameters in determining storm depositional patterns on the Eel shelf. (C) 1999 Published by Elsevier Science B.V. All rights reserved.