Hansen Dam and Reservoir was built by the U.S. Army Corps of Engineers, Los Angeles District and completed in September 1940. It is located in the City of Los Angeles at the confluence of the Big and Little Tujunga Washes along the northeastern edge of the San Fernando Valley. In conjunction with Sepulveda Dam and Lopez Dam, it is vital for flood risk management of portions of the San Fernando Valley and areas contiguous to the Los Angeles River. The primary purpose of the Dam is flood risk management. The Project is also authorized for recreation and can assist with water conservation when operated in conjunction with Los Angeles County through their spreading grounds just downstream from the Dam.
Hansen Dam and Reservoir includes the following elements: an earth-fill dam, a western saddle dike, and land that forms the reservoir when there is an impoundment due to rainfall runoff from the upstream watershed. The Corps reserves 162.7 acres of the 1,461.3 acre Dam and Reservoir area exclusively for routine maintenance of the Dam. The remaining 1,298.6 acres have been leased to the City of Los Angeles for recreational uses.
For detailed physical data and current project status information visit the Reservoir Regulation page. Additional information on Hansen Dam and Reservoir can be found in the Hansen Dam Basin Master Plan.
Keep yourself safe when visiting the many public facilities in the reservoir by being aware if the potential for storms is being forecast. The Reservoir is designed to hold back large quantities of water and can fill very quickly. Check the local weather forecast before enjoying the many recreational opportunities in and around the reservoir.
The Corps evaluates environmental effects of all actions taken at the Dam and in the Reservoir. Biological surveys are conducted in the Reservoir throughout the year by the Corps and the Corps partner agencies.
Many wildlife species are found within the Reservoir. The open water areas found in the Reservoir attract waterfowl and shorebirds such as great egrets (Ardea) and ruddy ducks (Oxyura jamaicensis). Riparian and upland habitats host a diversity of passerine species such as black phoebe (Sayornis nigricans) and California towhee (Melozone crissalis). Bat species are also present and use the Reservoir for roosting, breeding, or as year-round residents. Only two amphibians are common, including the California toad and Pacific tree frog. Dry upland areas host common lizard and snake species.
Native vegetation identified in the Reservoir includes sandbar, narrowleaf, and coyote willow (493.9 acres or 34.0% of the Reservoir), California sagebrush (146.4 acres or 10.1% of the Reservoir), black sage (4.3 acres or 0.3% of the Reservoir), and California broomsage (4.6 acres or 0.3% of the Reservoir).
The Corps engages in routine maintenance activities within the operational areas of the Reservoir year round to maintain the operational capacity of the project. As congressionally appropriated funding allows, the Corps works to upgrade aging structures and systems. Annual maintenance activities at US Army Corps of Engineers operated dams include grading of access roads, vegetation removal, and an annual safety inspection. In addition, the control house, gates, and all mechanical and electrical equipment is checked at each dam to make sure that it is functioning in accordance with the Dam Operations Manual. Graffiti removal, clearing of debris and sediment, and additional repairs are performed to maintain the facility.
Review Upcoming Proposed Actions
To review public notices on our upcoming proposed maintenance activities please visit the Public Notice postings page or click the “Public Notice” link found in the navigational side bar.
Questions, Concerns, Comments?
Let us know by clicking the “Contact” button in the navigation bar and choose Asset Management (Real Estate | Recreation) or Asset Management (Facility Operations | Maintenance) as the recipient.
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