San Geronimo Creek Habitat Enhancement Engineering Design Project

Coho salmon and steelhead once occurred in abundance in the San Geronimo Creek watershed and the mainstem has been specifically identified as one of the reaches in greatest need of rehabilitation. Landowners along the creek have also become increasingly concerned with nearby bank erosion and potential flooding of adjacent infrastructure in annual high flow events.

Stillwater engineered a restoration solution that provided critical habitat for fish while simultaneously protecting the integrity of adjacent privately-owned floodplains and creek-side banks. To achieve this balancing act, Stillwater staff:

  • collected new topographic data at three specific bank erosion sites;
  • developed hydraulic models in HEC-RAS for each site based on field-surveyed channel cross-sections and flow gage data to determine flow velocities, shear forces and flooding potential during different flow regimes and considering different proposed treatments;
  • conducted stability analyses to determine anchoring components and volume of boulders necessary to keep large wood in place during high flow events; and
  • developed a complete set of engineering design plans for each site, including existing conditions, temporary access, and proposed design and planting plans, along with site specific restoration details.

The San Geronimo Creek Habitat Enhancement Project highlights Stillwater’s broad expertise in engineering, geomorphology, fish biology and ecology that allow us to develop cost-effective restoration solutions that provide a benefit to humans and natural systems.


Location: San Geronimo Creek, Marin County, California

Clients: Marin County Department of Public Works and California Department of Fish and Wildlife

Project Manager: Joel Monschke

Project Lead(s)

Joel Monschke
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Work Products

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Based on ground-surveyed topography and bathymetry and HEC-RAS hydraulic modeling results, inundation maps were created that provided key information related to opportunities and constraints in terms of habitat enhancement and flooding potential.

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