Numerical model for analyzing the effects of sediment supply on river morphology and streambed characteristics
We are investigating the effects of different sediment supply regimes on the morphology and aquatic habitat of gravel-bed rivers in mountain basins. Sediment inputs to the river network in these environments range from periodic pulsed events of large magnitude (e.g., landslides and debris flows) to low-level chronic inputs (e.g., road drainage). The pulsed events tend to be natural, while the chronic inputs are commonly anthropogenic. Our goal is to inform managers of the range of sediment supply impacts and to evaluate the common perception that pulsed events are more detrimental to the aquatic ecosystem. Four cases of sediment supply are considered: 1) periodic pulses of fine material (e.g., debris flows in decomposed granite), 2) periodic pulses of coarse material (e.g., landslides in harder bedrock), 3) chronic supplies of fine material (e.g., roads or distributed soil creep and dry raveling) and 4) chronic supplies of coarse material (e.g., mining activity). Currently we are focusing on fine sediment moving primarily as bedload at flows below bank-full over an immobile coarse-grained bed. As part of this work, we evaluated the performance of available surface-based transport models. Predicted transport rates were compared to field measurements from gravel-bed rivers in Idaho. Results show that the Wilcock and Kenworthy (2002) equation performs best. We also have developed a sand conservation model based on filling the voids between coarse particles in a gravel bed. Numerical simulations were conducted coupling the conservation model with the Wilcock and Kenworthy equation using an extension of the MD-SWMS hydraulic model (McDonald et al. 2005). Performance of the transport and conservation models has been tested with data from laboratory experiments. Future modeling will initially compare the effects of cases 1) and 2) (chronic versus pulsed loads of fine sediment), as smaller particles are often implicated in degradation of aquatic habitats.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 1862 Sediment transport (4558);
- 1894 Instruments and techniques: modeling;
- 4558 Sediment transport (1862)