Sedimentation in the Lower Laguna-Mark West Drainage

Project Chief: Lorraine Flint

The Sonoma County Water Agency (SCWA) and the San Francisco District office of the U.S. Army Corps of Engineers (CORPS) have identified issues associated with sedimentation in the lower Laguna de Santa Rosa and Mark West Creek in Sonoma County. Human activities in the watershed over the last 200 years have accelerated erosion and sediment delivery to the Laguna reducing the water storage capacity of the floodplain and degrading the wetland function. To provide a foundation for evaluating sediment remediation approaches in the Laguna drainage, the USGS was requested by the CORPS to develop a phased approach to characterize and numerically simulate flow and sediment transport on floodplains and in channels of the Laguna de Santa Rosa and Mark West Creek using the RMA2 model. Along with the characterization of the main channel hydrodynamics, general sediment budgets and an understanding of floodplain processes are deemed necessary.

The study will address the management question of whether there has been a change in flood storage capacity for the lower Laguna-Mark West drainage, and the development of the conceptual understanding and numerical ability to answer design questions and what-if scenarios for future Corps sedimentation projects in the basin. This proposal will address these issues in the first phase of a study that will characterize flow and sedimentation processes within the study area by developing a conceptual model of floodplain processes and sedimentation, a sediment budget, measuring floodplain sedimentation and inundation, and extrapolating the results throughout the basin in GIS in order to evaluate the changes in flood storage capacity over time. To evaluate the numerical tools necessary for managing future basin sedimentation projects, and lay a foundation for future study phases, a 1-D calibrated hydrodynamic model will be developed for the Laguna-Mark West drainage with an overlying 2-D pilot reach that will be developed for sediment transport simulations.

Contact Information

Lorraine Flint
Office phone: 916-278-3000

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