by Pete Weisser

The Challenge

To give Congress and the State Legislature a clear vision of the Central Valley’s flood challenges and how the comprehensive study can help meet them, State and federal study partners this year compressed three volumes of technical analysis into a succinct 35-page report.

This interim report documents the magnitude of flood risks along the Sacramento and San Joaquin rivers and tells how the five-year, $21 million study, partnered by the U.S. Army Corps of Engineers and The Reclamation Board of California, proposes to develop systemic improvements in flood management through a watershed approach.

“This report is descriptive,” says Mike Bonner, Federal Project Manager for the comprehensive study. “It gives members of the State Legislature and Congress—some of whom may know little of our flood problems—an overview of the flood challenges here, describes how the study can identify solutions, and justifies investing significant Federal and State funds in a very worthwhile study.”

A History of Floods

Historically, flooding has been a recurrent reality in the Central Valley. Between 1850 and 1900, the Sacramento River basin was affected by 12 major floods, the report states, while the San Joaquin River basin experienced 16 major floods.

Flood management systems in the Central Valley were developed incrementally over many years in response to these floods.

After widespread flooding in 1907 and 1909, the “Jackson Report,” compiled by the California Debris Commission, proposed construction of the Sacramento River Flood Control Project, thus initiating coordinated construction of many levees, weirs, and bypasses in the Sacramento Valley.

Starting in the 1940s, multipurpose dams and reservoirs began providing storage for flood protection, water supply, recreation, and power generation. The current flood management systems in both river basins reflect the incremental development of flood protection projects and require extensive coordination among several agencies to operate and maintain.

Devastating Recent Floods

Between 1900 and 1999, the Sacramento and San Joaquin river basins experienced 13 destructive floods. Four of the most severe occurred in 1983, 1986, 1995, and 1997. They showed that the Central Valley’s farmlands and urban centers are at extreme risk.

“These four recent floods caused extensive damage in both basins and raised questions about the adequacy of the current flood management systems and land uses in the floodplains,” the report states.

Existing flood management systems functioned, preventing over $20 billion in damages, but the systems were clearly overtaxed. Combined damages from these recent floods exceed $1.6 billion. During the 1997 floods alone, damages in the Sacramento and San Joaquin River basins totaled $524 million.

Major storms throughout California caused record flows on many rivers, according to the report. In the Central Valley, the flood management systems for the Sacramento and San Joaquin rivers were stressed to capacity and beyond.

Reservoirs were tested to their limits. Levees proved vulnerable.

“Levees on the Sacramento River and its tributaries sustained two major breaks,” says the report, while many levees that survived needed major repairs. “On the San Joaquin River, levees failed in more than two dozen places.”

The post-flood assessment clearly presented the challenges facing federal, State, and local flood control officials. When the final Sacramento-San Joaquin River Basins Comprehensive Study is completed in 2002, system-wide flood management solutions will provide added protection for those who live along California’s two largest river systems.

Biggest Study in the West

“This is the largest study of its kind in the Western United States, and so far we’re making good progress,” said Mike Bonner, Project Manager for the Corps of Engineers. “We now have more than a dozen engineers, hydrologists, environmental scientists, and modelers working full-time on Phase II of the study.”

Tasks completed include a thorough assessment of four major recent floods—1983, 1986, 1995, and 1997—and identification of existing flood and environmental problems. The study team also has established study objectives, developed hydrologic and hydraulic models which are essential for analyzing flood potential on both river systems, and crafted a strategy to implement system improvements.

“Building on the flood data of recent years, the study team has constructed and calibrated ‘state of the art’ hydrologic and hydraulic models, which will allow us—for the first time—to address this Central Valley flood challenge system-wide.” says Yaeger.

“We’re midway through pilot studies to verify conceptual models of ecosystem functions which are related to flood flows. We are in good shape technically to develop and analyze the data we need to make improvements in the flood management systems of both rivers and their floodplains.”

Customized analytical tools developed for the study include an Ecosystem Functions Model for the rivers and floodplains and Geographic Information Systems (GIS) data. New digitized topographic data has been developed for the main rivers and tributaries to support the hydrologic and hydraulic models.

“The prospect of developing an Ecosystem Functions Model on this scale which is linked to hydrologic and hydraulic models and driven by data from GIS is as exciting as it is cutting edge technology,” says Jerry Ripperda, environmental lead for The Reclamation Board and DWR.

Flood and Environmental Issues

Taking an inclusive watershed approach, the study has identified and will address both flood problems and environmental issues.

Typical flood problems include:

• Flood management systems designed early this century lacked the capacity to convey peak floodflows experienced in the past two decades.

• Levee structural integrity is not reliable in some parts of the systems.

Environmental challenges include:

• Confining floodflows in reservoirs and between levees has caused loss of natural hydrologic and geomorphic processes, with degradation of fish and wildlife habitat.

• Funding has been often inadequate to mitigate for habitat loss.

In developing flood damage reduction and integrated ecosystem restoration measures, the study team will consider a wide range of solutions and strategies, both structural and nonstructural.

These include creating or improving bypass and levee systems and meander belts, reconstructing channels, discouraging future floodplain development, protecting and re-establishing natural flow processes, and integrating restoration of riverine habitat into improvements of the flood management system.

Public Has A Say

Public involvement plays a vital role in the study. During Phase I, study team members met with technical support groups to identify problems and potential solutions and with policy focus groups to identify policy issues and needs for policy change. In the fall of 1998, local support group meetings were held at 11 locations throughout the Central Valley to identify local concerns.

Upon initiating Phase II in the summer of 1999, study team members met with the general public at a series of meetings in the communities of Fresno, Modesto, Sacramento, Red Bluff, and Marysville.

Public and media interests were moderate, with modest attendance at most meetings and news coverage by valley newspapers including the Marysville Appeal-Democrat, Modesto Bee, and Merced Sun-Star. The format was that of an “open house” with exhibits and demonstrations, concluding with an “open mike” dialog, after initial briefings and poster sessions.

“I’d say the biggest surprise in the public meetings,” said Yaeger,” was that so many of the public were aware of the connection between flood management and ecosystem restoration. That nexus between flood protection and restoring the ecosystem is a major priority of our study and they seem to endorse that. They also seem to like the watershed approach taken by the study.”

Plans for Phase II

The plan of action for Phase II focuses on encouraging further public involvement, conducting feasibility-level assessments, developing basin master plans and a programmatic environmental document to support implementation.

“We will be working hard throughout this next year to ensure completion of specific planning documents in 2001,” says Yaeger.

Other Water Planning Studies

The Sacramento-San Joaquin River Basins Comprehensive Study is coordinated with other water planning programs, including:

• CALFED Bay-Delta Program, which is developing long-term plans to address water quality, water supply, Delta levee integrity, and ecosystem restoration issues in the Sacramento-San Joaquin Delta.

• Central Valley Project Improvement Act of 1992, which authorized modified operation of the Central Valley Project to restore and protect aquatic and waterfowl habitat in the Central Valley.

• Upper Sacramento River Fisheries and Riparian Habitat Management Plan, mandated by passage of SB 1086 and adopted by the State Resources Agency in 1989, to help restore fish and riparian habitat in the Upper Sacramento River.

• San Joaquin River Management Program, established in 1990, to resolve water use and environmental problems within the San Joaquin River system.

Keeping Congress Informed

Study leaders have made it a point to keep Central Valley flood control officials and State Legislators well-informed on the study. In September, they held a briefing in Washington, D.C. for members of California’s Congressional delegation. Congressional familiarity with the study may become important when funding proposals are made for projects stimulated by the study in 2002 and beyond.

Shared Funding

Of the comprehensive study’s total $21 million cost, $16.5 million for the feasibility planning effort is shared equally by the State and federal governments. The initial $5 million cost for the post-flood assessment and early model development was funded entirely by the federal government.

Final Result

After four years of research, analysis, and planning, the result in year 2002 is expected to be new master plans for flood management of both major river basins.

These master plans will be in the form of a programmatic environmental impact statement/environmental impact report for flood damage reduction and ecosystem restoration along both rivers. Subsequent documents on specific actions will address site-specific issues.

Specific actions which can produce immediate and effective flood damage reduction and ecosystem restoration
results will be identified and recommended for early implementation.

San Joaquin Challenges

Experience thus far indicates that many more challenges exist on the San Joaquin River than on the larger Sacramento River.

While the San Joaquin system has only a fraction of the flow capacity of the Sacramento, it is a more piecemeal “evolved” system with few bypass and overflow areas to relieve pressure on the main stem.

By contrast, the larger Sacramento River system is a more fully developed, multi-featured and coordinated flood management system, with an extensive system of weirs and bypasses to relieve flood pressures on the main channel adjacent to urban areas.

What are Hydrologic/Hydraulic Models?

These models are not the kind one builds from pieces of wood or plastic. They are computer programs constructed to analyze stream flows. They use historical data gathered over 100 years from stream gages and other river flow recording equipment.

The data is plugged into hydrologic and hydraulic equations that can predict such river behaviors as the maximum amount of water a river channel can carry, the water surface elevation in a channel, and the direction flood waters may follow if flows exceed channel capacity.

Accuracy of these models depend on the accuracy of the historical stream gage data and the accuracy and resolution of the topographic data.