RESERVOIR SEDIMENT MANAGEMENT LOS ANGELES COUNTY FLOOD CONTROL DISTRICT Presented by: Sterling Klippel, PE LA County Flood Control District Owns and operates complex flood protection and water conservation system that includes: • 14 major dams • 162 debris basins • 500 miles of open channel • 27 spreading grounds facilities Water Conservation San Gabriel River Water Conservation System Sediment Concerns • Fires accelerate sediment accumulation • Reduced reservoir capacity • Potential to block outlet works • Increased flood risk to facilities/communities downstream • Creates increased risk for dam safety Image Credit: NASA RESERVOIR SEDIMENT MANAGEMENT PROJECTS Devil’s Gate Dam and Reservoir Watershed Size: 31.9 sq. mi. Percent Burned: 68% (100% undev.) Original Capacity: 3.7 MCY Remaining Capacity: 1.3 MCY Planned Sediment Removal: 1.7 MCY Image Credit: Arroyo Seco Foundation Construction Period: 2018 – 2023 Cogswell Dam and Reservoir Watershed Size: 39.2 sq. mi. Percent Burned: 90% Original Capacity: 19.8 MCY Remaining Capacity: 16.8 MCY Planned Sediment Removal: 2.6 MCY Construction Period: 2018 – 2020 Big Tujunga Dam and Reservoir Watershed Size: 82.3 sq. mi. Percent Burned: 87% Original Capacity: 10.1 MCY Remaining Capacity: 8.0 MCY Planned Sediment Removal: 2.0 - 4.4 MCY Construction Period: 2019 – 2023 Pacoima Dam and Reservoir Watershed Size: 28.2 sq. mi. Percent Burned: 96% Original Capacity: 9.8 MCY Remaining Capacity: 4.3 MCY Planned Sediment Removal: 3.0 - 5.2 MCY Construction Period: 2020 – 2024 San Gabriel Dam and Reservoir Watershed Size: 202.7 sq. mi. Percent Burned: N/A Original Capacity: 86 MCY Remaining Capacity: 71 MCY Planned Sediment Removal: 5 MCY Construction Period: 2019 – 2024 A SUSTAINABLE DEVIL’S GATE A Sustainable Devil’s Gate Following extensive community outreach and involvement, the Board approved the Devil’s Gate Reservoir Sediment Removal and Management Project. Protecting Communities Community‐Based Solutions Enhancing Native Habitat and Recreation Protecting Communities • The Station Fire caused 1.3 MCY of additional sediment to enter Devil’s Gate Reservoir. • Reservoir does not have adequate capacity for a major storm event. • Until sediment is removed, there is significantly increased flood risk to 650 parcels and 447 structures along the Arroyo Seco. Project Overview Restores flood protection capacity and reduces flood risk • 1.7 MCY project maximum • 800,000 CY annual maximum Establishes a permanent maintenance area for annual sediment removal • Reduces need for major sediment removal project in the future Community‐Based Solutions Since 2010, the Flood Control District has been listening and working with cities and community groups on efforts to address their concerns regarding the Project. As a result of these efforts, the project has been significantly enhanced: No truck traffic or Low emission trucks that staging on residential meet EPA standards streets 70+ acres of enhanced Access to trails during non- open space with native work hours and weekends vegetation with new wayfinding signage Enhancing Native Habitat and Recreation Objectives • Enhance recreational opportunities throughout Hahamongna Watershed Park. • Restore habitat to attract a wide diversity of wildlife. • Create high quality nesting habitat for least Bell’s vireos and southwestern willow flycatchers. • Provide a more pleasing experience for birdwatchers, hikers, equestrians, and those that want to connect with nature. Enhancing Native Habitat and Recreation Enhancing Native Habitat and Recreation Enhancing Native Habitat and Recreation Thank You Sterling Klippel, PE Principal Civil Engineer Stormwater Engineering Division .