Location: Watershed Physical Processes ResearchTitle: Simulation of morphological changes due to dam removal Author
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/1/2013
Publication Date: 9/1/2013
Citation: Ding, Y., Elgohry, M., Altinakar, M., Wang, S. 2013. Simulation of morphological changes due to dam removal. In: Khan, A.A. and Wu, W. Sediment Transport: Monitoring, Modeling and Management. Nova Science Publishers, New York. p 213-238. Available: www.novapublishers.com/catalog/product_info.php?products_id=41291 Interpretive Summary: This book chapter gives a literature review on numerical models and their applications for impact assessment of dam removal on sediment transport and morphological changes in alluvial rivers. The well-established 1-D channel evolution model, CCHE1D, was used to demonstrate the impact of the Marmot dam removal in the Sandy River, Oregon, on its hydrological and geomorphological environments. This model was carefully validated by reproducing the morphological changes induced by the reservoir sediment releases after the dam was removed. Then, a long-term simulation of river flows and sediment transport was carried out to predict the sedimentation processes in the river downstream by giving a synthetic 10-year-long hydrological hydrograph. It is found that the rate of erosion and deposition in the later five years is higher than in the first five years, because the discharges in the later five years are greater than in the first five years. The trend of the changes depends on the sequence of the selected water years. It is also found that the variations of water surface around the knickpoint follow the bed elevation changes. The long-term impact assessment on morphological changes in the Sandy River is reasonable and can be used for managing and planning river sedimentation after the dam removal. As a future topic of the research, it suggests further developing a shock-capture scheme for the hydrodynamic model of CCHE1D in order to predict the initial sediment transport right after the dam removal was triggered.
Technical Abstract: In this chapter, a brief review of numerical models and their applications for impact assessment of dam removal on sediment transport and morphological changes in alluvial rivers is given. As an example, a one-dimensional river flow and sediment transport model, CCHE1D, is applied to assess morphological changes in a reach of the Sandy River, Oregon due to the Marmot Dam removal in the summer of 2007. The model parameters (e.g., bed roughness coefficient, sediment adaptation length, sediment transport capacity) are first calibrated by ensuring that simulated bed changes after one-year of dam removal within the study reach are in good agreement with the field observations. After the successful model calibration, the model is applied to assess long-term morphological changes in response to a synthetic hydrograph consisting of 10 years selected from historical storm water records. The long-term assessment results on morphological changes are reasonable and can be used for managing and planning river sedimentation after the dam removal.