Effect of Local Slope on Bed Load Transport in the Surf Zone
Abstract
Energetics models for sediment transport in the surf zone do not account for gravity-induced transport that is not collinear with fluid motion. These models only allow for a single value of local bed slope to be specified in the cross-shore direction. While in theory, energetics models have predictive capability for both cross-shore and long-shore sediment transport they are typically only used to predict cross-shore transport in practice. A suite of three-dimensional discrete particle computer simulations of bed load transport was performed for a variety of flow conditions and a range of bed slopes (both parallel and perpendicular to the flow) common to the surf zone. In the case where the bed slope is perpendicular to the fluid motion, for example, cross-shore wave-generated oscillatory flow over a bed locally sloping long shore, the long shore component of the bed load transport rate is linearly related to the net cross-shore component for slopes up to 10 degrees. At higher long shore slopes, the long shore transport rate grows nonlinearly with the slope and can exceed the cross-shore rate at slopes approaching the angle of repose. Such transport has important implications for the modeling of smaller scale, three-dimensional bed features (from megaripples to rip channels). Previous modifications to the Bagnold/Bowen/Bailard energetics-based bed load transport formulae can be expanded to include the effects of an arbitrary local bed slope (by allowing for the input of both cross-shore and long shore local slopes) using a vector formulation that can be easily tested with velocity and bathymetry measurements commonly obtained in field experiments. Research supported by the Coastal Dynamics Program of the Office of Naval Research and the National Ocean Partnership Program. >http://www4.ncsu.edu/unity/users/j/joe/public/</a>
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFMOS21C..07C
- Keywords:
-
- 4255 Numerical modeling;
- 4546 Nearshore processes;
- 4558 Sediment transport