Sacramento River Flood Control Project Weirs and Flood Relief Structures

Sacramento Valley has a history of floods and management of floods that goes back as long as people have populated the region. Prior to flood management, the valley floor would be blanketed by seasonal runoff nearly every year; the Sacramento Valley was once nicknamed the “inland sea.” This tendency to flood results from the geography of the region as well as the weather.

The occasionally large amounts of rain that fall in the surrounding Coastal ranges and the relatively steep Sierra Nevada mountain ranges produce rapid surface water runoff to the Sacramento River. The amount of this surface water runoff can be quite large, depending on the amount of rainfall, snow melt, and soil moisture of the watershed. Fast water flowing from the mountains is blunted by the relatively shallow grade of the Sacramento River south of the city of Red Bluff, and would often overtop the river banks.

In addition, The Sacramento River would begin depositing sediment in the more shallow grades that would often alter its direction of flow. In order to control these storm flows that would otherwise flood farmland and cities, the Sacramento River Flood Control Project (the Project) was created.

The Project was designed with the understanding that runoff from many of the storm events experienced in the Sacramento River watershed cannot be contained within the banks of the river. Nor could this flow be fully contained within a levee system without periodically flooding adjacent property. Thus, the Project was designed to occasionally spill through a system of weirs and flood relief structures into adjacent basins.

These basins are designed to contain flood waters and channel them downstream, to eventually be conveyed back into the Sacramento River near Knights Landing and Rio Vista. Dry weather flows are contained within levees near the river banks and land within the flood basins is then used for agricultural purposes.