5.1D – Dams and Levees – Removal
Remove dams or levees which are unsafe, unwanted, and/or obsolete, with careful consideration of alternatives.
For the purposes of this management measure, dams are defined as constructed impoundments that are either (1) 25 feet or more in height and greater than 15 acre-feet in capacity, or (2) 6 feet or more in height and greater than 50 acre-feet in capacity. Levees are embankments or shaped mounds constructed for flood control or hurricane protection (USACE, 1981). Floodwalls or slurry-walls are longitudinal structures used to reduce flooding. Setback levees are levees set back a distance from the banks of a river or stream, these flood control structures can be constructed without disturbing the adjacent natural channel vegetation (riparian habitat), and cross section of the stream or river channel. Levees act like small earthen dams but are typically not subject to constant hydrostatic forces that dams are built to withstand. This is due, in part, to the changing hydraulic head behind levees, especially in California’s Mediterranean climate. Channelized rivers are typically contained between levees.
Dam and levee removal re-connects the stream to its floodplain by allowing the stream to periodically overtop its channel banks which reduces stream velocities by dissipating sediment and water over the floodplain. Groundwater storage is increased in the floodplain soils which may reduce downstream flooding (by decreasing the volume of water flowing in the stream channel). Reduction in high velocity stream flows prevents downstream shoreline erosion and channel incision. Aquatic habitats become more complex i.e. provide a range of temperature and flow conditions as a result of dam and levee removal. More complex aquatic habitats means greater ecosystem resiliency.
The negative environmental effects of dam and levee removal include temporary sedimentation to adjacent water bodies, reduced surface water storage which can increase downstream flooding, and if impounded sediments contain toxic chemicals, the release of contaminated sediment can cause unnecessary exposure to humans and the environment. The environmental benefits of dam and levee removal include increased groundwater recharge (in some cases this can reduce downstream flooding); reduced streambed and shoreline erosion; enhanced aquatic and wildlife migration corridors; and restored riparian and aquatic ecosystem functions.
Planning and Design
- Cost/benefit analysis is an important first step in the watershed planning process; benefits and cost of removing the dam or levee must outweigh the benefits and cost of maintaining the dam or levee.
- Balance environmental, social, cultural, and economic needs and mitigate for lost benefits. Where applicable, consider non-structural alternatives to flood control, water storage, and power generation. Assess changes to flood hazard designation as a result of the removal.
- Conduct assessments of stream channel stability and capacity. Determine appropriate stream channel dimensions for changing hydrologic conditions. Model hydraulic effects upstream and downstream of the project area. Refer to MM 5.2B - Stream Channel Modification, Flow Maintenance for more information on modeling stream hydraulic effects.
Remove the hydrologic barrier that disconnects the stream to its floodplain
Levee Removal using the String-of-Pearls Approach
Prioritize removal of strategic sections of levee slopes where:
- the stream channel is not highly incised,
- overtopping stream banks is probable during a 2-5 year flood event, and
- adequate floodplain area is available for periodic inundation by flood waters.
Gradually (over a period of years to decades) release water stored in the reservoir behind dam. After the water is released, the sediment stored behind the dam can be removed using either passive or active restoration. Finally demolish and remove the dam wall.
Soil Excavation for both Levee and Dam Removal
Prior to removal of sediment, perform a representative amount of soil testing to determine if the sediment contains toxic concentrations of chemicals. If the sediment is hazardous to humans and/or the environment then completely remove the sediment. Use silt curtains or other temporary sediment erosion management practices during excavation activities, see MM 3.2D – Urban: Construction, Grading and Excavation for more information on temporary sediment erosion control measures.
Based on the quality of the sediment, project budget, and time allotted for complete restoration, the following techniques can be implemented;
- Complete removal (excavate and transport) of all sediment accumulated behind dam;
- Partial removal (excavate and transport) of a portion of sediment within the stream channel dimensions; or
- Passive restoration where none of the sediment is removed; high flow events erode a new channel(s) through the sediment (Wunderlich et al., 1994).
Habitat and Stream Channel Restoration
For more information on habitat restoration refer to MM 6B – Restoration, Rehabilitation, and Mitigation of Wetlands and Riparian Habitats.
Programs and Permits
The following federal requirements may apply to dam or levee removal:
- Rivers and Harbors Act Permit
- FERC License Surrender or Non-power License Approval
- National Environmental Policy Act (NEPA) Review
- Endangered Species Act Section 7 Consultation
- Magnuson-Stevenson Act Consultation
- National Historic Preservation Act Compliance
The following state requirements might apply to dam or levee removal:
- Clean Water Act (CWA) Section 404 Dredge and Fill Permit
- Coastal Zone Management Act Certification
- Waterway Development Permits
- Dam Safety Permit
- California Environmental Quality Act
- Historic Preservation Review
- Resetting the Floodplain
- Clean Water Act (CWA) Section 401 Water Quality Certifications
Demolition and building permits may also be required for dam removal. Individual state and local governments may have additional requirements as well (USEPA 2007).
- Federal Energy Regulatory Commission (FERC) through the Federal Water Power Act (FPA) regulates the licensing of dam construction and re-licensing of large dams used for hydropower. The FERC re-licensing process (18 CFR Parts 2, 4, 5, 9, 16, 375, and 385) allows for the equal consideration of beneficial uses which may have not been considered when the dam was originally constructed (before the Clean Water Act, Endangered Species Act, and other environmental laws were passed). In fact, under FPA section 4(e) FERC must give equal consideration to energy conservation; the protection and enhancement of fish and wildlife habitat, the protection of recreational opportunities, and the preservation of other aspects of environmental quality including water quality under SWRCBs Clean Water Act Section 401. FERC must operate and maintain a dam so that the best mix of beneficial uses are considered and managed.
- California Department of Water Resources Fish Passage Improvement Program staff meet with local, State, and federal agencies and stakeholder partners to plan and implement projects to remove barriers that impede migration and spawning of anadromous fish species. This program’s Web site has a link to a table of dams removed in California.
- Department of Homeland Security, Federal Emergency Management Agency, National Dam Safety Program (NDSP) is a partnership of the states, federal agencies, and other stakeholders to encourage individual and community responsibility for dam safety. Established by the Water Resources and Development Act of 1996, three components include grant assistance to States, and Dam Safety research and training.
- Department of Water Resources (DWR), Division of Safety of Dams conducts investigations of selected dams, which include a comprehensive review of all pertinent material contained in the Division’s files, a visual project inspection, technical studies when necessary, and preparation of a comprehensive report.
- DWR, Delta Levees Program is responsible for improving the flood protection and ecosystem resources of the Delta Levee System. DWR sponsors locals, who undertake various improvement projects to achieve these ends for the benefit of Delta landowners, State Water Project contractors, and the ecological communities which depend on vital natural habitats. DWR manages these projects in cooperation with the Department of Fish and Game, the Reclamation Board, and other federal, State, and local agencies. The Delta Levees Program is an active participant in the CALFED process.
- DWR, FloodSAFE is a sustainable integrated flood management and emergency response system throughout California that improves public safety, protects and enhances environmental and cultural resources, and supports economic growth by reducing the probability of destructive floods, promoting beneficial floodplain processes, and lowering the damages caused by flooding.
- DWR, Levee Repair web pages provide a wide range of information on California's levee system and the efforts the State is undertaking to evaluate the stability of the system and implement critically needed repairs designed to protect our communities, farmlands, and infrastructure.
- California Department of Fish and Wildlife is responsible for conserving, protecting, and managing California’s fish, wildlife, and native plant resources. To meet this responsibility, the law requires any person, State, or local government agency, or public utility proposing a project that may impact a river, stream, or lake to notify the Department before beginning the project. If the Department determines that the project may adversely affect existing fish and wildlife resources, a Lake or Streambed Alteration Agreement is required.
- The Clean Water Act Section 401 – Certification and Wetlands Program administered by Regional Water Quality Control Boards (RWQCBs), review projects that require a federal permit under CWA section 404 or that involve dredge or fill activities that may result in a discharge to waters of the United States. This is to ensure that the State’s interests are protected on any federally permitted activity occurring in or adjacent to waters of the State. Detailed information about CWA section 401 in California, including a description of the program, resources, legal background information, proposed projects, and links, are described on the SWRCB Web site.
- NRCS, USDA Service Centers provides the address of a USDA Service Center and other Agency offices serving your area along with information on how to contact them. The local NRCS staff can provide technical assistance to small dam owners for operator and maintenance activities.
- US Army Corps of Engineers 404 Permitting Program, Sacramento District / Regulatory Program administers and enforces Section 10 of the Rivers and Harbors Act of 1899 and Section 404 of the Clean Water Act. Under Section 10, a Corps permit is required for work on structures in, over or under navigable waters of the United States. Under Section 404, a Corps permit is required for the discharge of dredged or fill material into waters of the United States. Many waterbodies and wetlands in the nation are waters of the United States and are subject to the Corps' Section 404 regulatory authority.
- US Fish and Wildlife Service (USFWS) Section 7 of the Endangered Species Act directs all Federal agencies to use their existing authorities to conserve threatened and endangered species and, in consultation with the Service, to ensure that their actions do not jeopardize listed species or destroy or adversely modify critical habitat. Section 7 applies to management of Federal lands as well as other Federal actions that may affect listed species, such as Federal approval of private activities through the issuance of Federal permits, licenses, or other actions.
- USFWS, National Fish Passage Program uses a voluntary, non-regulatory approach to remove and bypass barriers. The Program addresses the problem of fish barriers on a national level, working with local communities and partner agencies to restore natural flows and fish migration. The Program is administered by National and Regional Coordinators, and delivered by Fish and Wildlife Management Assistance Offices, with their 300 biologists located across the Nation.
- Clearinghouse for Dam Removal Information is an unbiased living receptacle of information about technical, fiscal and social aspects (pro and con) of dam removal, including cases where a decision is made to retain the dam. The purpose of the Clearinghouse is to allow all parties involved in dam removal decisions to share experiences, learn successful techniques and avoid repeating mistakes. In particular, it is trying to capture the "gray literature" that is transiently available when a dam removal is taking place or being considered.
- Friends of the Earth, American Rivers, and Trout Unlimited. 1999. Removing Dams that Don’t Make Sense - Removing Dams Has Many Benefits. Highlights the removal of 25 dam removal projects nationally and two projects in California: Butte Creek (four dams were removed) and Lake Christopher Dam on Cold Creek.
- American Rivers and Trout Unlimited. 2002. Exploring Dam Removal: A Decision Making Guide. This guide is divided into four areas of consideration (a) ecological, (b) economic, (c) societal, and (d) technical/engineering. Each section provides a brief overview of topics shown through experience to be useful in determining if a dam should be removed; a more thorough set of questions is available in the Appendix.
- American Rivers. 2000. Paying for Dam Removal: A guide to selected funding sources. This paper goes through the need for dam removal funding; describes the roles and process for various funding options using federal, state, and local government programs and private sector funding; provides several case studies; and elaborates on the process for developing an economic analysis to determine the amount of funding a dam removal project could cost.
- American Rivers. Data Collection: Exploring Dam Removal. This fact sheet contains various data sources that can be used to help start a dam removal project.
Friends of the Earth (FOE), American Rivers, and Trout Unlimited. 1999. Dam Removal Success Stories: Restoring Rivers through Selective Removal of Dams that Don't Make Sense. Accessed June 2007.
USACE. 1981. Low-cost shore protection, final report on the shoreline erosion control demonstration program (Section 54). U.S. Army Corps of Engineers. Washington, DC.
USEPA. 2007. National Management Measures Guidance to Control Nonpoint Source Pollution from Hydromodification. EPA 841-B-07-002. U.S. Environmental Protection Agency, Washington, DC.
Washington Department of Fish and Wildlife. 2004. Stream Habitat Restoration Guidelines. Downloaded on August 11, 2008
Wunderlich, R.C., B.D. Winter, and J.H. Meyer. 1994. Restoration of the Elwha River ecosystem and anadromous fisheries. Salmon Ecosystem Restoration: Myth and Reality. Proceedings of the 1994 Northeast Pacific Chinook and Coho Salmon Workshop. American Fisheries Society, Corvallis, OR.