Devastating floods are almost annual occurrence in the west and in California. With the anticipated sea level rise and other impacts of a changing climate, particularly heavy winter rains, flood management is increasingly critical in California. Compounding the issue are man-made flood hazards such as levee instability and stormwater runoff.
With such issues in mind, flood management includes giving constricted rivers more breathing room by setting back levees, reducing floodplain development and giving equal weight to environmental and economic factors in making management decisions.
Flood Management Issues
Flood management is often in conflict with water supply practices and needs. Flood control managers must keep enough reservoir storage space available to manage floods during heavy precipitation, but water suppliers focus on storing enough water to protect against drought.
Additionally, flood control involves many different local, state and federal agencies [see list at bottom of the page], and their management philosophies change with the political and economic times. The state also has many local flood management agencies responsible for the day-to-day operations and maintenance of facilities, development and implementation of flood management and stormwater drainage plans, and coordination with other state and federal agencies.
Flood Management Infrastructure
Upstream dams have done much to reduce flooding, but there is broad concern about the adequacy of downstream levees in providing protection.
In the Sacramento-San Joaquin Delta, there are approximately 1,100 miles of levees protecting 700,000 acres of lowland. In the Suisun Marsh, there are approximately 230 miles of levees protecting over 50,000 acres of marshland. Some of these levees, however, are unstable 100-year-old earthen mounds of packed mud.
In California’s Central Valley, a growing population has pushed subdivisions into floodplains previously leveed off for agricultural use, often without recognizing the inadequate level of protection provided by the existing flood management infrastructure. This echoes a DWR report from 2005 that said the Central Valley’s flood protection system is “deteriorating and, in some places, literally washing away.”
“The Central Valley’s flood protection system is “deteriorating and, in some places, literally washing away,” Calif. Dept. of Water Resources.”
Flood Mitigation Efforts
In 2006, California voters approved Proposition 1E and Proposition 84, which provided a $4 billion general obligation bond to pay for work including levee repairs in the Delta and Central Valley, improved flood protection for cities and stormwater flood projects.
Through DWR’s FloodSAFE California Initiative, local, regional, state, tribal and federal officials have teamed up to create sustainable, integrated flood management, floodplains and emergency response systems throughout California. Goals include providing a 200-year level of protection to all urban areas in the Sacramento-San Joaquin Valley by the end of 2025.
Local components of these flood management efforts also are in place throughout California.
Levee protection against floods in California levees is much lower than in pre-2005 New Orleans- Calif. Dept. of Water Resources.
Local Flood Management Efforts
In Sacramento, the Sacramento Flood Control Project consists of a system of levees, overflow weirs, pumping plants and bypass channels. In times of high flows, the Sacramento and Yolo bypasses carry many times the amount of water left in the Sacramento River.
The Central Valley has a flood protection network that includes 23 reservoirs with flood detention space and more than 1,760 miles of federally designated levees, overflow weirs and channels. In addition, there are a series of dams were built on the western slope of the Sierra Nevada for both flood control and water supply. These include Shasta Dam on the Sacramento River, Oroville Dam on the Feather River and Folsom Dam on the American River.
In the more arid Southern California region, flash floods prompted formation of the state’s first flood control district in 1915 in Los Angeles. Today, the Los Angeles County Department of Public Works in coordination with the U.S. Army Corps of the Engineers operates 14 dams, 115 debris basins, 26 groundwater recharge facilities, 524 miles of major channels, 29 pump plants, 77,990 catch basins, and 2,800 miles of tributary storm drains.
The state also has more than 2,600 miles of levees and sloughs that fan out from the San Pablo Bay northeast of San Francisco up to Sacramento and Stockton. Many of the state’s levees are simply mounds of river mud constructed in the 1800s and not designed to protect buildings.
Despite progress, flood management still faces significant obstacles. Many floodplains already are developed and providing rivers with more room to roam is controversial, expensive and nearly impossible. Virtually all of the natural floodplains along the Los Angeles River are urbanized. Much of the city of Sacramento lies in the historic floodplain. Other areas throughout the state are experiencing rapid development.
Looking ahead, there is also the as yet unknown impact of climate change and rising sea levels.
Key Agencies Involved in Flood Management
The U.S. Army Corps of Engineers (Corps) is the primary federal flood management agency, developing guidelines for flood management storage in federally-funded reservoirs and monitors reservoir operations. The Corps also constructs flood management projects, operates multiple-purpose projects, and provides resources, equipment and personnel for emergency floods.
The National Weather Service issues weather forecasts and flood warnings. It helps communities establish flood warning systems and conducts flood hazard analyses and provides other technical assistance.
The Federal Emergency Management Agency (FEMA) administers the National Flood Insurance Program, disaster planning and recovery programs. FEMA works closely with states and communities and provides financial and technical assistance, flood hazard maps and data to better manage floodplains.
The California Department of Water Resources operates the State Water Project, runs the state-federal Flood Operations Center and assists the NWS in flood forecasting. It is responsible for the operation and maintenance of the Sacramento and San Joaquin flood management projects. DWR funds flood management projects outside the Central Valley, carries out the state’s flood plain management laws and coordinates the floodplain management aspects of FEMA in California.
The Central Valley Flood Protection Board cooperates with the Corps in the planning, construction, operation and maintenance of flood management projects in the Central Valley. Once a project is completed, the board holds the federal government harmless, accepts legal responsibility for its maintenance and then turns the maintenance responsibility over to a local agency or DWR. The board also controls, through a permitting process, activities and development in state designated floodways.
The Board’s 2017 Central Valley Flood Protection Plan is designed to improve flood protection for more than 1 million Californians and $70 billion in homes, businesses and infrastructure. The plan uses farmland to create new flood space or flow capacity that would come from new setback levees and expansions at the Yolo Bypass and Paradise Cut, off the San Joaquin River.
The plan’s implementation is estimated to cost $20 billion during a 20- to 25-year period. DWR included three possible fee mechanisms: reactivating the Sacramento-San Joaquin Drainage District fee, a landowner-based river basin assessment and a proposed state flood insurance program.
The California Office of Emergency Services may allocate funds for investigation, estimates, reports and repairs regarding disaster recovery financial assistance for flood management works that do not come under the provisions of another authority. It administers Federal Emergency Management Agency’s hazard mitigation program in California.