Historical flooding along California's Cosumnes River, including extensive flooding in 2023, breached levees, overwhelmed roads, and resulted in fatalities. To help address these challenges, Verdantas Eco Engineering (formerly cbec eco engineering) worked with the California Department of Water Resources (DWR) to evaluate multi-benefit floodplain rehabilitation opportunities that could reduce flood risk, improve water supply resilience, and enhance ecosystem function throughout the watershed. The effort brought together local partners, including Reclamation District 800, Omochumne Hartnell Water District, Sacramento Valley Conservancy, and Sloughhouse Resource Conservation District, to explore solutions that balance flood management, groundwater sustainability, and environmental restoration goals. 

The Verdantas team developed hydrologic and hydraulic models to better understand how water moves through the Cosumnes River system and surrounding floodplain. These datasets were integrated into the Ecological Floodplain Inundation Potential (EcoFIP) framework, which was used to identify physical opportunities for floodplain reconnection and evaluate potential restoration concepts. Working collaboratively with project partners, the team assessed alternatives including levee setbacks and modifications, using advanced modeling to estimate how each concept could influence floodplain inundation patterns and reduce flood risk.  

To better understand future watershed conditions, the project evaluated both observed flow data and climate-adjusted hydrologic scenarios. A decision-scaling process was used to assess system vulnerabilities under varying degrees of warming and changes in precipitation, providing insight into how restoration strategies may perform under a range of future conditions. The team also integrated EcoFIP results with a fine-scale groundwater model to evaluate how reconnecting floodplains could influence groundwater recharge and long-term water supply resilience 

Several conceptual restoration alternatives were developed and analyzed to quantify potential flood risk reduction benefits. Through EcoFIP and hydraulic modeling, DWR and project partners gained a clearer understanding of where floodplain rehabilitation could help alleviate pressure on existing levee systems while supporting broader watershed objectives. Final deliverables included a comprehensive digital package of models, analyses, and planning information to support future decision-making and implementation efforts. 

The project demonstrates how flood resilience can be strengthened by considering both infrastructure and natural watershed systems together. By combining floodplain analysis, hydrologic and hydraulic modeling, climate resilience planning, and groundwater evaluation, Verdantas helped identify opportunities to reduce flood risk while creating lasting benefits for water resources, ecosystems, and the communities that depend on them. 

Project Outcomes:

• Evaluated floodplain reconnection opportunities using the EcoFIP framework.  
• Developed hydrologic and hydraulic models to assess flood risk reduction concepts.  
• Assessed potential groundwater recharge benefits associated with floodplain restoration.  
• Evaluated watershed vulnerabilities under multiple climate scenarios.  
• Supported DWR and local partners in identifying multi-benefit floodplain rehabilitation strategies.