Hydraulic and Channel Migration Studies

Project Lead: Stanislaus County Office of Emergency Services

Potential Project Partners:
RD 2091, Gomes Lake JPA, City of Modesto, City of Newman, City of Patterson

Short Project Description:
Two regional studies (mainstem San Joaquin River flood hydraulics and channel migration) and three focused hydraulic studies are needed to better inform flood management in the Mid SJR Region.

Long Project Description:
Two regional studies are required to advance flood management planning within the Mid SJR Region’s planning area. First, updated baseline hydraulic analyses of flood conditions on the mainstem of the San Joaquin River in the Mid SJR Region’s planning area are needed to inform site-specific studies of flood hazards and better identify flood hazard mitigation opportunities. The analyses will include a range of flood events, such as the 2-, 10-, 25-, 100-, and 200-year events and will largely or entirely rely on available models and hydrology as developed for the CVFPP. A report on this study will provide a regional evaluation of the level of performance of the flood management facilities and produce a set of recommendations for improvements and a strategy for pursuing them. Second, as a counterpart to the hydraulic analyses, a channel migration study within the same area will also be conducted to identify under current (baseline) conditions approximately where, and by what degree, channel movement is anticipated to occur, creating challenges and opportunities for flood management. The results of the channel migration study will be used to inform the recommendations in the hydraulic study.

These two regional studies will provide the backdrop for a set of three site-specific studies to address flood risks within the region. While the regional studies will not include all of the relevant information needed for the site-specific studies, they will provide key contextual information. The site-specific studies will include: 1) RDs 2091 and 2063, including the City of Modesto’s wastewater treatment plant on Jennings Avenue and the Gomes Lake project; 2) the City of Patterson’s wastewater treatment plant; and 3) the City of Newman’s wastewater treatment plant. Each of these site-specific studies is described in further detail below.

The RD 2091/RD 2063 area contains considerable critical infrastructure (e.g., the Modesto wastewater treatment plant and Gomes Lake) and is the most highly populated area protected directly by project levees. The characteristics of flood flows that would occur in the event of a breach in either district need to be identified. There is the potential that RD 2091 is dependent on the RD 2063 levees for protection as well as on its own levee system. A breach in RD 2091 could also possibly cause flood waters to back into RD 2063 to some extent. The characteristics of flood flows from RD 2063 into RD 2091, and vice versa, also needs to be thoroughly understood in order to identify practical containment options and an effective flood fight plan for the districts. This study would include obtaining the current topography and bathymetry from new sources as needed to supplement existing datasets. The study report will include specific recommendations to reduce flood risks and inform an effective flood fight plan for the RDs.

Hydraulic studies for the Newman and Patterson Wastewater Treatment Plans (WWTPs) would confirm water elevations at which there is a significant threat to those facilities and the characteristics of flood water movement in the event that 1) water elevations rise above the eastern boundary fence line at the Patterson plant, or 2) either the Newman Wastewater Treatment Plant flood control levee or the Newman Wasteway embankment fails. This detailed information would allow development of better trigger levels for actions to protect infrastructure and better plans for maintaining service if either of these events were to occur.

Current and planned studies completed by DWR under the Central Valley Flood Protection Plan (CVFPP) and other programs should be accessed initially for information relevant to the above issues. Any current relevant information generated by those studies can be used as a starting point for the studies described above.

Unique Project Characteristics:
None specified.

Project Status Pre-planning
Project Cost $200,000
Project Timeframe 1-5 years
Cost-sharing Undetermined
Multi-benefit Project Yes
Types of benefits The project would contribute to our understanding of flood risk and, therefore, would help to improve flood risk management.
Source of Project The project was an outcome of the emergency response technical memorandum prepared by the Mid SJR RFMP project team. Stakeholders participating in workshops during the fall of 2013 also suggested that this project be considered.


Unique Project Characteristics:
None specified.