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Prediction of Impacts Associated with Reservoir Sediment Management

Project ID: 1262
Principal Investigator: Blair Greimann
Research Topic: Sediment Management and River Restoration
Funded Fiscal Years: 2004 and 2005
Keywords: None

Research Question

* Can Reclamation develop environmentally acceptable, efficient methods to manage sediment in our reservoirs?

* As Reclamation's dams age and as sediment continues to fill our reservoirs, what are the best tools and methods to predict the impacts associated with a variety of sediment management strategies?

Need and Benefit

As Reclamation's dams age, sedimentation becomes a major hindrance to their sustained use. More efficient methods to decrease sedimentation are necessary because mechanical dredging costs can quickly become unmanageable. In addition, as some dams become obsolete or not cost effective, Reclamation must decommission them in the most efficient manner possible. In both of these cases, allowing the river to transport sediment can be the most cost effective solution. To plan sediment releases appropriately, a model must be used to predict the possible impacts. These impacts may be positive or negative. For example, the sediment releases may improve habitat in sediment starved reaches downstream of dams. However, un-managed sediment releases may increase the flooding potential or temporarily destroy habitat.

Potential large releases of sediment will occur during the removal of Elwha and Glines Canyon Dams on the Elwha River near Port Angeles, Washington and the removal of Matilija Dam near Ventura, California. Several small dams are also being considered for removal or have been removed. Some examples are Saeltzer Dam and Battle Creek Diversion Dams in California, and Savage Rapids Dam in Oregon. Black Canyon is an example of dam where sediment releases may be necessary to extend the dam's useful life. East Park Dam is an example of a dam with severe sedimentation problems and where sediment releases could improve its water storage capacity.

A large obstacle to releasing sediment downstream is the uncertainty associated with its impact. Managers and stakeholders do not want to have a liability risk as a result of dam operation. Therefore, they may use a more costly mechanical or structural alternative to eliminate risk. However, such practices may cost millions of dollars and take money away from other necessary functions Reclamation performs. These problems will increase in both frequency and magnitude as dams age. Reclamation must have the best tools available to be prepared to face such problems. A better numerical model will reduce the uncertainty associated with large sediment releases and potentially save millions of dollars.

Contributing Partners

None

Research Products

Independent Peer Review

The following documents were reviewed by qualified Bureau of Reclamation employees. The findings were determined to be achieved using valid means.

Journal article on sediment analysis of dam removal (final, PDF, 105KB)
By Blair Greimann
Report completed on May 30, 2014

The movement of ┬┐nite amplitude sediment accumulations is studied using a simple advection-diffusion relation derived from the sediment continuity equation and using some heuristic reasoning. The movement of a ┬┐nite amplitude sediment accumulation is found to be strongly diffusive with a small advection component due to the increase in transport rate of the sediment accumulation relative to the transport rate of the original bed material.
Keywords: sediment movement, dam removal

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Chapter on Sediment Analysis of Dam Removal in Reclamation Sedimentation Manual (final, PDF, 336KB)
By Blair Greimann
Report completed on May 30, 2014

This chapter of the Erosion and Sedimentation Manual focuses on the sediment management aspects of dam removal and avoids the discussion of the legal and institutional issues. This Erosion and Sedimentation Manual chapter also briefly describes the linkages between sediment management, dam removal engineering, and the effects on the aquatic ecosystem
Keywords: dam removal, sediment transport

This information was last updated on October 25, 2014
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