Skip directly to: Main page content

Delta Solutions

Mulitmedia Collection

Delta Solutions

Center for Watershed Sciences

Watershed Sciences Building - 1st Floor
University of California, Davis
One Shields Avenue
Davis, CA 95616

(530) 754-9133
FAX (530) 754-9364

Contra Costa Times

Readers' Forum: The Delta: Managing the Inevitable

May 2, 2009. Jeffrey Mount and Jay Lund

FIGHTING OVER the peripheral canal has obscured a greater and more immediate issue for those who live, work, and play in the Delta: the deteriorating state of its levees.

It is an inconvenient scientific certainty that the Delta's 1,100 miles of levees are fragile and that much of the Delta will inevitably change as a consequence of their failure. Every day, every year, despite the valiant efforts of Delta reclamation districts and land owners, the levees compact or subside from their own weight.

Rodents burrow into them, and waves and currents erode them. Levees often fail under ordinary circumstances, as with Jones Tract in June 2004. On the levees' land side, tilling and oxidation of peat-rich Delta island soils have led to staggering subsidence.

Land behind these levees is more than 20 feet below sea level in much of the western and central Delta. The land continues to sink today, increasing pressures on the levees and increasing their costs of repair.

Outside the levees, the sea level is rising. This rise is well-documented, and all projections for the future indicate that it will accelerate.

The flow of water into the Delta also is changing. This stems from a shift in runoff patterns, with more intense winter flooding due to climate warming. Both processes raise risks to levees.

To complete the picture, a major earthquake is long overdue in the Bay Area near the Delta. Extensive research involving scientists from around the world concludes that earthquakes pose considerable risk to the levees, particularly in the western Delta. There is roughly a two-in-three chance of such an earthquake in the next 25 years. And the Delta levees — unlike almost all critical infrastructure in California — are not designed to resist earthquakes.

Unfortunately, we cannot reasonably build our way out of this problem. Raising the height of the levees does little to stem the earthquake risk because of their weak foundations. And major construction throughout the Delta would be prohibitively expensive. Just raising the levees to a basic federal standard — roughly six inches — would cost more than $1.4 billion with only a small reduction in risk of failure. This level of investment, with only a nominal return, would be a poor business decision.

One of our students at UC Davis, Robyn Suddeth, has completed a peer-reviewed study of whether it makes economic sense from the perspective of a landowner, business, or the state to reduce risks by upgrading the levees. Her results are surprising. Taking failure probabilities into account, it does not make economic sense, relative to land and asset values, to upgrade the levees on any deeply subsided Delta island or to repair as many as a quarter of the islands once they have failed.

The combined weight of all physical and economic factors points to one conclusion: the Delta will undergo significant change through the permanent flooding of islands. Most of this change will occur in the deeply subsided western and central Delta, where low land values and high failure risk coincide. These islands may fail and be abandoned by their owners individually over time, like Franks Tract (1938), Mildred Island (1983), and Liberty Island (1998). Or several may fail together from floods or earthquakes.

In an era of large state and federal budget deficits, hard choices will have to be made about which islands to repair.

The good news is that with strategic investments in levees — rather than spreading the investments equally, everywhere — most, if not all, of the Delta will remain a wonderful place for farms, fish, and recreation for generations to come. But strategic investments require acknowledgment of the risks and the development of new levee policies to address them.

To help ease the transition to the "new" Delta of the 21st century, policies are needed that prioritize levee improvements, mitigate the financial impact to landowners whose islands flood, and develop long-term, sustainable funding mechanisms for levee maintenance and repair.

As we learned from Hurricane Katrina, nature and economics ultimately prevail over wishful thinking and political indecision.


Mount is a professor of geology and Lund is a professor of civil and environmental engineering at the University of California, Davis. They are members of a multidisciplinary research team that co-authored Comparing Futures for the Sacramento-San Joaquin Delta for the Public Policy Institute of California. The report can be downloaded at


Comparing Futures for the Sacramento-San Joaquin Delta

Jay Lund, Ellen Hanak, William Fleenor, William Bennett, Richard Howitt, Jeffrey Mount and Peter Moyle. July 2008. Public Policy Institute of California.


For over 50 years, California has been pumping water through the Sacramento-San Joaquin Delta for extensive urban and agricultural uses around the state. Today, the Delta is ailing and in urgent need of a new management strategy. This report concludes that building a peripheral canal to carry water around the Delta is the most promising way to balance two critical policy goals: reviving a threatened ecosystem and ensuring a reliable, high-quality water supply for California.

Envisioning Futures for the Sacramento-San Joaquin Delta

Jay Lund, Ellen Hanak, William Fleenor, Richard Howitt, Jeffrey Mount and Peter Moyle. February 2007. Public Policy Institute of California.


California's Sacramento-San Joaquin Delta is widely perceived to be in crisis today: its levee system is fragile, many of its native species are declining rapidly, and it lacks strong governing institutions to deal with its problems. In its current state, the Delta is unsustainable for almost all stakeholders. This report provides a comprehensive, scientifically up-to-date analysis and outlines several alternative management strategies for the Delta.

Current and Long-Term Effects of Delta Water Quality on Drinking Water Treatment Costs from Disinfection Byproduct Formation

Wei-Hsiang Chen, Kristine Haunschild, and Jay R. Lund. 2009. Circulating draft.


This study explores the current and long-term effects of Delta export water quality on drinking water treatment cost and residual public health risk from disinfection byproduct (DBP) formation. Appropriate treatment options and strategies were discussed based on water quality constituents of concern. The costs of selected treatment technologies were estimated and applied for current and future conditions for different export locations with projections of future water quality. Overall, drinking water treatment costs would be lower for Sacramento River water. With roughly 1.5 million acre-foot (af) per year of Delta water used for urban water supplies, the drinking water treatment cost differences of taking water from the south Delta and the Sacramento River upstream could amount to $30 to $90 million per year currently, and possibly rise to $200 to $1000 million per year in the future, with lower water quality and use of the Delta likely to rise to 2 million af annually. Currently DBPs are manageable with Delta supplies within treatment standards, while sea level rise and western island failures would make treatment of Delta water for urban use more difficult and expensive. Bromide from seawater, combined with total organic carbon is a particularly problematic precursor of DBPs. With sea level rise and western island failures, waters drawn directly from the Delta will likely become increasingly risky to public health and less desirable as a conventional water source.

Habitat Variability and Complexity in the Upper San Francisco Estuary

Peter B. Moyle, William A. Bennett, William E. Fleenor, and Jay R. Lund. July 2009. Circulating draft.


The San Francisco Estuary is a complex estuarine ecosystem. Variability in environmental conditions, especially in the Delta, once made it highly productive for native biota. Present conditions discourage desirable species, providing a rationale for restoring estuarine variability and complexity. Achieving a variable, more complex estuary requires establishing seaward gradients in salinity and other water quality variables, diverse habitats throughout the estuary, more floodplain habitat along inflowing rivers, and improved water quality. These goals in turn encourage policies which: (1) establish flows that create a tidally-mixed, upstream-downstream gradient in water quality; (2) create slough networks with natural channel geometry; (3) improve flows from the San Joaquin River; (4) increase tidal marsh habitat, including shallow (1-2 m) subtidal areas, in both fresh and brackish zones of the estuary; (5) create/allow large expanses of low salinity (1-4 mg/l) open water habitat in the Delta; (6) create a hydrodynamic regime in which salinities range from near-fresh to 8-10 mg/l on a regular basis to discourage alien species and favor desirable species; (7) create habitat conditions that support higher and more variable site-specific native species diversity; (8) establish abundant annual floodplain habitat, with large areas that flood in less frequent wet years; (9) reduce inputs of pollutants; and (10) improve temperature regimes in large areas so temperatures rarely exceed 20 degrees celcius during summer and fall. These actions collectively provide a realistic approach to achieving flow and habitat objectives to benefit desirable species. Some of the goals are likely to be achieved as the result of sea level rise, climate change, and levee failures, but habitat, flow restoration and export reduction projects will enhance a return to a more variable and more productive ecosystem. This finding has widespread support in ecological theory and observations from other systems, but making quantitative predictions of change is not yet possible.

Levee Decisions and Sustainability for the Sacramento-San Joaquin Delta

Robyn Suddeth, Jeff Mount, Jay Lund. 2009. Circulating draft.


The Sacramento-San Joaquin Delta's fragile levees are subject to several physical realities that make them increasingly prone to failure. State planners face the challenge of preparing for future Delta flooding. This study presents an economic method for approaching the evaluation of Delta island levee upgrades and repairs. A Levee Decision Analysis Model (LDAM) is applied to the question: How should the state economically prioritize levee upgrade and repair efforts in the Delta? We focus on 34 major agricultural islands that make up most of the Delta's Primary Zone and include all non-urban subsided islands. This initial analysis indicates that it is economically optimal to not upgrade all 34 Delta islands examined, mostly because levee upgrades are expensive, but produce little improvement in levee reliability. When we assume increased effectiveness of upgrades, it becomes optimal to upgrade some islands. Other islands are never optimally upgraded, even under the most optimistic scenario. Our analysis also suggests that from an economic perspective, taking into account land and asset values, it is not cost effective to repair between 18 and 23 of these islands when they fail. When property values for all islands were doubled in a sensitivity analysis, only four islands of those originally not repaired become cost effective to repair. The LDAM model presented here is a useful approach for Delta policy-makers. It provides a quantitative framework for addressing several relevant questions regarding reasonable levee upgrade and repair investments. These initial results may act as a springboard for discussion, and the LDAM model as a working framework for developing an optimal strategy. An important and inescapable conclusion of this analysis is that maintaining the current Delta landscape is unlikely to be economical from a business or land use perspective.

Policy Implications of Permanently Flooded Islands in the Sacramento-San Joaquin Delta

Robyn Suddeth. August 2009. Circulating draft.


The Sacramento-San Joaquin Delta is in a state of inevitable transition. Physical and financial pressures are likely to transform parts of the Delta into open water within the next 100 years. Because flooded islands have different habitat, water quality, and hydrodynamic implications depending on location, depth, orientation, and other physical factors, the state may decide to intentionally flood one or more Delta islands in an effort to better manage the Delta?s ecosystem and valuable water supplies. This paper outlines three sets of near term actions the state would have to take to begin transitioning towards intentional island flooding, and discusses legal and political challenges to those actions. Several key findings include the following: (1) amendments to California?s water code and revisions to the Delta Land Use and Resource Management Plan may help the state ensure the legal authority to differentiate levee policies within the Delta; (2) permits for a first, experimental flooded island will likely require the State Water Resources Control Board to revise the Delta Water Quality Control Plan to allow for more short-term flexibility and deal with conflicting ecosystem and water supply uses; and (3) the state may want to prepare mitigation plans for private landowners on neighboring islands whose levees could face new threats of erosion and/or seepage from a nearby flooded island in order to avoid inverse condemnation lawsuits. If the state decides to shift its levee policies in the Delta, serious consideration will need to be given these and additional common, regulatory, statutory, and constitutional laws.