Spatial and Temporal Connections Between Sediment Delivery and Resuspension Potential along the California Coast
Abstract
During storm events, the fluvial processes that discharge sediment and the oceanographic processes influencing dispersal of that sediment should be much more strongly coupled for small coastal watersheds than large watersheds. If this coupling of fine-grained sediment delivery and dispersal is significant, different dispersal rates and processes may be expected on the shelves off small rivers than would occur off large river systems. We have examined the oceanic forcings present on the shelf during flood events (the period during and immediately following peak discharge events) on rivers draining small coastal watersheds of California. Hydrologic data from the river mouth USGS gauge and oceanographic data from a nearby NDBC buoy were compared for the Eel, Salinas and Santa Ana Rivers. Although there are geographic differences between the systems, strong coupling is observed between river discharge, wind stresses and direction and wave size and period for all sites. Because waves likely influence the dispersal of recently delivered near-bed sediment, we also evaluated wave-induced shear stresses during river discharge events. Although there is elevated potential for resuspension (wave-induced shear stresses greater than the critical shear-stresses needed to resuspend silts and clays), of fine-grained material during and following these discharge events, the events do not fully account for the annual resuspension potential. For example, during and in the 48 hours following large discharge events from the Santa Clara River, wave-induced bottom shear stresses surpass the critical threshold more than 50 percent of the time. While this is important, it only accounts for 2/3 of the total period when wave-induced resuspension was possible in our record. The remaining times occurred during storm events that did not produce discharge events from the river, indicating that there is also great potential for sediment remobilization all along the California shelf during times without large new inputs from the rivers.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMOS23A1629F
- Keywords:
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- 3022 Marine sediments: processes and transport;
- 4219 Continental shelf and slope processes (3002)