Sediment Management Investigation

Project Lead: River Partners

Potential Project Partners:
DWR, CVFPB, flood management agencies relevant to the Upper SJR RFMP and Lower SJR/Delta South RFMP

Short Project Description:
Complete a study that identifies sediment-induced chokepoints along the San Joaquin River in the planning area, the dynamics that create them, and potential actions to improve flood conveyance in those areas.

Long Project Description:
This project would include several analyses to better inform sediment management in the planning area. If specific flood hydraulic analyses for the mainstem of the San Joaquin River in the Mid SJR Region’s planning area have been completed prior to the initiation of this study, those models and results would be relied upon adequate to generally identify hydraulic chokepoints created by sedimentation during flood events with stages in the vicinity of the levee crest profile, assuming all flows are contained by the current levees. If those hydraulic studies have not yet been completed, this study would rely on new applications of the existing Central Valley Floodplain Evaluation and Delineation Program (CVFED) model of the San Joaquin River and representations of flood hydrology adequate for the study purpose.

To determine how the channel has changed over time, recent topographic and bathymetric data represented in the hydraulic model would be compared to data from existing sources, including the 1917 Debris Commission Survey, construction of the project levees (1955), and Sacramento and San Joaquin Basins Comprehensive Study (2002).

Lastly, a field survey would be completed to gather San Joaquin River sediment data for current and future study purposes. With the assumption that the river is capacity-limited in delivering sediment into and out of the Mid SJR Region’s planning area, grain size data collected as part of this study would be combined with available channel geometry data and used to estimate upstream sediment inflow to the region, outflow from the region, and typical transport capacities for reaches within the study area. The grain size data could also be used for potential future channel migration analysis, sediment transport modeling, and/or evaluation of dredge material disposal options, not included as part of the current study. Identification of apparent areas of erosion and deposition in the field can cross-check the desktop chokepoint analysis and provide a basis for estimates of the volumes of sediment in the study reach that have been contributed by bank erosion in recent years and sediment that has been stored in the channel as deposits during a similar time frame. Data collected and estimated in the course of this study will be used to develop an approximate sediment budget and a conceptual model of sediment transport dynamics for the San Joaquin River between the Merced River and the Stanislaus River. Based on the information developed through the activities described above, sediment management recommendations would be made for the San Joaquin River to improve flood conveyance within the Mid SJR Region’s planning area.

Unique Project Characteristics:
None specified

Background Information:
1917 Debris Commission Survey, construction of the project levees (1955), and Sacramento and San Joaquin Basins Comprehensive Study (2002)