Factors and Processes Affecting Delta Levee System Vulnerability
Steven Deverel, Sandra Bachand, Scott Brandenberg, Cathleen Jones, Jonathan Stewart, Paolo Zimmaro
- Large-scale, state investment in levee upgrades (> $700 million since the mid-1970s) has increased conformance with applicable standards; however, accounts conflict about corresponding reductions in the number of failures.
- Modeling and history suggest that projected increases in high-flow frequency associated with climate change will increase the rate of levee failures.
- A reappraisal of seismic threats resulted in updated ground motion estimates for multiple faults and earthquake-occurrence frequencies.
- Estimates of the consequences of future levee failure range up to multiple billions of dollars. Analysis of future risks will benefit from improved description of levee upgrades and strength as well as consideration of subsidence, the effects of climate change, and earthquake threats.
- Levee habitat ecosystem benefits in this highly altered system are few. Better recognition and coordination is needed among the creation of high-value habitat, levee needs, and costs and benefits of levee improvements and breaches.