Southport Multi-Objective Flood Control and Habitat Restoration Project

Southport has been a cornerstone project for cbec, spanning multiple years, and with various successful project team configurations. This West Sacramento Area Flood Control Agency (WSAFCA) project’s goal was to set back reaches of the Sacramento River Levee through West Sacramento to provide a 200-year level of flood protection, valuable ecological habitat benefits, and high recreational value on the restored floodplain.

cbec provided geomorphic and hydrodynamic modeling services, as well as ecological habitat design for aquatic and terrestrial species. Our primary role was to analyze hydraulic and geomorphic conditions at the site, assess the potential for levee and channel erosion and deposition, and estimate sedimentation impacts for the preferred design alternative, which included levee setback and floodplain lowering. To accomplish this, cbec collected sediment transport data (bed and suspended load) as well as ADCP (Acoustic Doppler Current Profiler) discharge measurements on the Sacramento River over a range of flow conditions. These data were used in the development and calibration of a 2-dimensional hydrodynamic sediment transport model (DHI – MIKE 21C) that was employed to assess various feasibility and design aspects of the levee setback project. Specifically, the model was used to characterize the existing sediment regime and long-term geomorphic function (erosion and deposition trends) as well as site specific erosion control design. Using the model and the geomorphic assessments, cbec established how the site evolved historically, which informed the design of the setback levee relative to the sediment transport regime.

While the construction photos show a very harsh, barren environment currently, the artistic rendering demonstrates that, once completed, a dense riparian forest will rapidly establish.

Key to this plan was the use of ecohydraulic modeling to optimize the design. Our findings enabled the engineering of flood management solutions that are geomorphically sustainable while restoring the floodplain’s ecological function. cbec was also an integral member of the restoration team and led the physical design of the floodplain restoration that incorporated engineered wood structures to provide floodplain complexity.

Working with our project partners, cbec developed ecological design criteria that maximized high-value riparian habitat for terrestrial species, and rearing habitat and refugia for various special-status fish species, including juvenile salmonids. cbec staff provided construction observation and water quality monitoring during initial implementation (fall 2018), as well as construction support during restoration design, and final implementation during the summer and fall of 2019.

In 2020, the Institute for Sustainable Infrastructure awarded the Envision Platinum Award to the Southport project. The Envision sustainable infrastructure framework assesses project sustainability across five categories: Quality of Life, Leadership, Resource Allocation, Natural World, and Climate and Resilience. In 2021, this project received the American Council of Engineering Companies, California (ACEC California) Engineering Excellence Honor Award in Water Resources.

Southport was featured in the April 2020 edition of the American Society of Civil Engineers’ (ASCE) Civil Engineering Magazine. Read here.

We were on site at Southport in January 2023 to capture how the structures handled the deluge brought in by the area’s record heavy rainfall. We are happy to witness the levees working just as engineered.
The video above displays a 2-dimensional hydrodynamic model output of the south offset area along the Sacramento River. These model simulations characterize the inundation dynamics for offset areas which are helpful in characterizing the habitat quality for salmonids at flowranges that tend to occur during critic times (i.e. outmigration / rearing) during their life cycle. The ability to use the model to optimize the habitat for target species present a significant opportunity to design for the best possible ecological outcomes.