The Sacramento River Levee Setback Project: Using 2-dimenisional
Models to Design Ecologically Functional Floodplains
John Stofleth1, Chris Bowles1, Doug Shields1, Sergio Jimenez2,
Kenric Jameson3
1Presenter: cbec eco engineering, 2544 Industrial Boulevard, West Sacramento, CA 95691
(916) 662-0122
2HDR Engineering, Sacramento, California
3West Sacramento Area Flood Control Agency, West Sacramento, California
Abstract
Floodplains that are regularly inundated for extended periods during certain times of the year are important for their high production of organic matter and invertebrates as well as for the provision of seasonal spawning and/or rearing habitat for native fishes. Contemporary researchhas identified criteria for the flow associated with such floodplains. Studies have hypothesized that there is very little remaining floodplain in California’s Central Valley, due to the combination of flow regulation, channel incision and levee construction. As a result of development on floodplains, there may be few areas floodplains can readily be restored without either dramatic changes in reservoir management, levee setbacks, or substantial alteration of floodplain topography. Those areas where floodplains can be restored should be high priorities for the restoration community since they offer floodplain function benefits across a broad range of flood magnitudes and support essential ecosystem functions and anadromous fish habitat.
One such site is adjacent to a 4-mile reach of the Sacramento River downstream of the City of Sacramento, where a major levee setback is proposedas a part of a multi-objective flood control and habitat restoration effort. This project represents an important opportunity for combining better flood management with significant ecological restoration.
In our presentation, we will discuss the multi-disciplinary approach employed by cbec to integrate hydraulic modeling with geomorphic interpretation to maximize the restoration benefits of this levee setback project. Our approach utilized the 2-dimensional hydrodynamic and morphologicalmodel MIKE21C to develop a geomorphically-based analytical tool for assessing the timing, duration, location, depth, and flow direction of floodplain inundation under existing and setback conditions for a 12-mile reach of the Sacramento River. Our assessment supported recommendations for restoration actions to optimize geomorphic function and increase and improve floodplainhabitat. Our analysis also examined the potential for unintended consequences for erosional and depositional effects of the setback project on floodplain management. The benefits of using a 2-dimensional hydrodynamic model as a tool to inform restoration design for specific species of concern will be emphasized in our presentation. Important understandings about the timing, extent, and duration of floodplain inundation are achieved using our approach, and this information is extremely valuable in developing restoration designs.
We will also discuss how these types of levee setbacks are representative of significant opportunities for the future. These projects are one of the few ways of achieving both increased flood protection and habitat restoration and in turn provide multiple benefits to society. They are illustrative of one of the most promising solutions to the current levee integrity/flood management crisis in California.
Stofleth_John.doc