Abstract:
Reservoir drawdown is an expensive and one of the most important operations for dams
/reservoirs running, maintenance and operations. On Elwha river, Glinde Canyon and Elwha
dams were suggested to be removed for the purpose of preserving the ecosystem and
anadromous fisheries. To understand the effect of dam removal on water quality and
sediment transport of the bed, an experiment was conducted by the U.S National Park
Service, U.S Geological Survey, Bureau of Reclamation and Lower Elwha Klallam Tribe.
This experiment was conducted in April 1994. The water level of the Elwha River has
lowered 18ft in 14 days, and sediment transport in all the corresponding cross-sections was
noted.
Performing these experiments on actual structures is always time-consuming and
uneconomical. For this purpose, many researchers have been using various tools like Dream
1, Flow 3D and HEC-RAS to simulate the phenomena and approach to the best results they
can. In this research, we simulated this experiment on HEC-RAS using Ackers & White.
Simulation performed in HEC-RAS is 1D, the cross-sectional comparison is showing that
the trends of erosion and deposition using Ackers & White are similar. The main purpose of
our research is to predict sediment erosion in this delta and compare Ackers & White with
actual experiments.
In the final part of this research, we simulated this experiment using two more formulas,
Yang and Laursen. The formulas in HEC-RAS are selected according to the bed gradation of
the river. Their comparison is showing that Ackers & White is giving us better results in this
scenario.
