Opportunities and challenges of setback levees as a means to address flood control concerns and restore natural processes and native habitats

The Bear River Levee Setback Project at the confluence of the Bear River and Feather River in southwestern Yuba County, California is part of a program of flood control improvements being implemented in this area that has experienced several devastating floods in the last 50 years. The key benefits of the project are replacement of an aging levee with a new levee constructed to modern standards on known foundation conditions, reduction of upstream water surface elevations during high flow conditions by expanding the floodplain, and restoration of fish and wildlife habitat in the expanded floodplain. Construction of the setback levee and grading of the restoration area was completed in November 2006; restoration planting began in November 2006 and will continue through fall of 2007. Approximately 600 acres of agricultural land is being planted with native habitat types, including riparian forest and scrub, shaded riverine aquatic, and grassland/savanna. This restoration serves the dual purpose of fulfilling specific mitigation needs for upstream flood control improvements, as well as overall habitat enhancement benefits in this primary location at the confluence of a major Central Valley river and one of its main tributaries. Construction of setback levees represents a key shift from traditional flood control protection improvements that have typically resulted in loss and degradation of natural riverine processes and the habitats they support. Setback levees are becoming a favored engineering solution for increasing concerns regarding levee integrity, and they provide a prime opportunity to restore natural floodplain processes and conduct large-scale habitat restoration. This project serves as a valuable case study in overcoming the challenges associated with the complex multi-disciplinary nature of such endeavors and their wide range of objectives and constraints.