Katrina’s legacy21 March 2011
Since the days of the Californian gold rush the Central Valley’s levees have played an important flood protection role in the US. However, following the devastating aftermath of Hurricane Katrina, the integrity of such flood protection defences have been placed under close scrutiny. Melinda Terry from the California Central Valley Flood Control Association gives more details
Since the levees damaged by Hurricane Katrina in New Orleans in 2005 have been repaired and improved, the Sacramento region now has one of the lowest estimated flood protection levels compared with other river cities in the US.
The two largest rivers in California, the Sacramento and San Joaquin rivers run through the Central Valley, draining an area of more than 17,000km2 of Northern California into the San Francisco Bay. The second largest river on the Pacific coast, the Sacramento River has an average annual discharge of about 849m3/sec.
The Sacramento River has always served as an important transportation route for its indigenous people during the gold rush, and even today. Early settlers seeking their fortune in California’s gold rush initially built levees to protect their communities and fertile farmland from flood waters. A by-product of the thriving hydraulic mining industry using high-pressure water jets was the build-up of large silt deposits in the riverbeds of the Central Valley which posed serious flood risks. To keep the water velocity high enough to scour away the sediment, levees in the Central Valley were built very close to the river channels.
Hydraulic mining is now a relic of the past but the system of narrow levee channels it left behind is a legacy that requires constant maintenance and investment to keep up with the erosive forces of the river. Today, these same levees protect large cities, productive farmland, state highways, railroad lines, energy transmission lines, natural gas reserves, and a water conveyance system that supplies water to more than half of the state’s population. Altogether, these Central Valley levees protect more than US$47B of infrastructure.
The Sacramento River Flood Control Project, originally authorised by Congress in the Flood Control Act of 1917, was built throughout the first half of the 20th century with a single objective – flood control. Today, the Central Valley is protected by a complex system of federal, state, and local flood control projects with numerous reservoirs, channels, levees, bypasses and related facilities. The reservoirs help to regulate river flows to levels that the flood control system can handle in most years.
Evolve to survive
The 21st century has brought a broad array of competing demands for the resources of the Sacramento River watershed. In order for the system to survive this century, it must evolve to meet not only the paramount demand for flood protection, but also accommodate ecosystem improvements, providing a reliable water supply, and increasing opportunities for recreation. Additionally, the impacts of climate change and sea level rise may further challenge system performance. A comprehensive, integrated, and sustainable set of solutions must be developed and implemented to transition this single objective system conceived in the early 20th century into a multi-objective system designed to meet the competing demands of the 21st.
The flood damage resulting from Hurricane Katrina, a Sacramento-San Joaquin Delta levee failure on a dry sunny day in 2005, and a State of Emergency declared by Governor Arnold Schwarzenegger in 2006, have collectively resulted in California planning for and investing in greater flood protection for the Central Valley. Despite constant news about the fragility of some of the Central Valley’s levees, particularly those in the Delta, and limited state and local investment in levee improvements over the past 25 years, significant increases in levee reliability have been achieved.
In February 2006, following sustained heavy rainfall and runoff, Governor Schwarzenegger declared a State of Emergency for California’s levee system. He signed Assembly Bill 142 commissioning up to US$500M of state funds to evaluate and repair state/federal project levees. This declaration was intended to prevent the potential for catastrophic consequences of Hurricane Katrina-like proportion. More than 100 of the most critical levee repair sites have already been completed, with others in process and still more sites being identified.
In 2006, the voters of California passed the Disaster Preparedness and Flood Prevention Bond Act (Proposition 84) and the Safe Drinking Water, Water Quality and Supply, Flood Control, River and Coastal Protection Bond Act (Proposition 1E). Together these bonds fund flood control projects to protect homes and prevent loss of life from flood-related disasters, including levee failures, flash floods and mudslides. That same year, the State Legislature also passed legislation requiring the preparation of a Central Valley Flood Protection Plan (CVFPP) by 2012. The CVFPP will document and assess current performance of the state-federal flood protection system in the Sacramento and San Joaquin Valleys and make recommendations to improve its integrated flood management system.
As local flood control managers, we believe the state’s plan should focus on three primary goals:
• Public safety and welfare – As the paramount duty of the state of California and its flood protection partners, implement flood protection and risk reduction measures that minimise the flood threat to human life as well as the threats to homes, property, and critical public infrastructure in urban, rural communities and agricultural areas.
• Sustainability – Develop and adequately fund flood protection and risk management projects that improve economic viability, minimise project life-cycle costs, and also consider compatibility with the ecosystem.
• Project implementation – Projects should be designed and implemented through a partnership between the local agencies, the state, and the US Army Corps of Engineers. Each partner should seek opportunities to apply permit and approval processes appropriate for the complexity and risk associated with each project. While it is recognised that projects may be implemented in stages, the whole system should be considered through funding authorisation and implementation.
The Central Valley Flood Control Association is committed to working with the state to identify a set of flood protection and risk management goals for the Central Valley, which will allow everyone to make improvements together. For the system-wide flood protection improvements to be successfully implemented, we believe urban and rural communities as well as agricultural areas must all be considered in the identification, evaluation, and prioritisation of investments for flood protection in relation to the system-wide performance and benefits needed today.
Melinda Terry is the Executive Director of the California Central Valley Flood Control System, Manager of the North Delta Water Agency. Email: [email protected]