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S&T Project 20102 Final Report: Debris Clogging Assessment at Dams

Information was collected on debris clogging and debris management of spillway and outlet works structures at various Bureau of Reclamation (Reclamation) dams to identify data trends and key research needs. A short survey was sent to each Reclamation Area Office for information on debris occurrence, debris type and size, location of debris accumulation, interaction of sediment with debris, cost of debris management, and mitigation and monitoring techniques. Survey responses were also received for various facilities from Tennessee Valley Authority and Federal Energy Regulatory Commission. Reclamation results show that excessive debris occurs during flood events at 70% of reported facilities and during normal operations at 22% of reported facilities. Debris typically arrives during the beginning of high flows events such as spring runoff or heavy rain events and often during spring months. Burn events and extreme hydrological events often contribute to excessive debris. Debris loads consist most frequently of deadfall trees (88%) and vegetative debris (65%) with 78% of facilities reporting debris in the medium to small size range. Submerged debris typically starts as surface debris and then sinks rather than moving through the reservoir along the bed. Once debris is no longer floating, its eventual fate is largely unknown. Twenty-two percent of Reclamation respondents indicated that a facility currently has notable issues with sediment impacting outlet structures. Large debris removal is typically conducted physically by crane for debris near the dam or saw-cutting and hand removal for debris deposited on rip rap or banks. Debris management costs are generally 5-10% of operating and maintenance budgets, but direct and indirect costs can become very high when an urgent issue is detected.
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Generation Effort S&T Project 20102: Debris Clogging Assessment at Dams
Location Name Western US
Type Uploaded file(s)
File Type PDF
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Publication Date
Update Frequency not planned
Last Update Monday, October 5th, 2020

Disclaimer

The findings and conclusions of this work are those of the author(s) and do not necessarily represent the views of the Bureau of Reclamation.