Water Resources Collections and Archives
When the levees break: Relief cuts and flood management in the Sacramento-San Joaquin Delta
- Author(s): Fransen, Lindsey
- Ludy, Jessica
- Matella, Mary
- et al.
The Sacramento-San Joaquin Delta is one of California’s most important geographic regions. It supports significant agricultural, urban, and ecological systems and delivers water to two-thirds of the state’s population, but faces extremely high risks of disaster. Largely below sea level and supported by 1,100 miles of aging dikes and levees, the Delta system is subject to frequent flooding. Jurisdictional and financial disincentives to better flood planning prevent coordination that might otherwise reduce both costs and damages. This study highlights one possible flood mitigation technique called a relief cut, which is an intentional break in a downslope levee to allow water that has overtopped or breached an upslope levee to drain back into the river. This flood management technique is "smart" when located in appropriate areas so that floodwaters can be managed most efficiently and safely after a levee break.
We identify four key constraints and make four recommendations for flood management planning. The constraints are: 1) Perception of flood risk -- The public believes that levees will protect them from all flood events; 2) Perverse incentives -- For reclamation districts to finance levee maintenance and flood planning, they must encourage development in flood risk areas to collect assessment fees; 3) Litigation threat -- Agencies remain vulnerable to litigation after a flood which is a disincentive for taking action because no one wants the blame; and 4) Reimbursement uncertainty -- Historical flood accounts demonstrate local entities are not always reimbursed for their expenditures which discourages quick action during a flood. We recommend the following actions for agency officials to endorse and the public to support: 1) Acknowledge that levees will fail and plan accordingly; 2) Explicitly plan for emergencies such as relief cuts before the flood occurs; 3) Support interagency cooperation, and 4) Apply Full Cost Recovery concept from the European Union Water Framework Directive.