Lower Corte Madera Creek Improvement Study Project

Three projects evaluated creek improvements in Lower Corte Madera Creek from the downstream end of the concrete channel in Ross to the bay. They were:

• A hydraulic and geotechnical assessment of the current condition of the levee and creek system. It was conducted by the Marin County Flood Control District (District) to:
  • Assess the need for future projects
  • Identify potential project concepts that could qualify for final design and construction funding from the Local Levee Assistance Program (California Department of Water Resources) or other sources
  • Identify and provide recommendations for improvements
  • Link to assessment: https://marinflooddistrict.org/documents/project-conditions-hydraulic-evaluation-of-the-corte-madera-creek-levees-october-2019/ 
• A concept-level design and layout of a "geomorphic dredge" approach to dredging in the lower creek, conducted by the District. This nature-based approach was designed to be in equilibrium with the daily tidal prism which could result in more sustainability and reduced need to do maintenance dredging, fewer impacts, lower cost due to lower volumes, and be more appealing to regulatory agencies due to less impacts.
  • District staff and consultants completed a first draft concept layout.
  • The approach was designed for sustainability, but it may not achieve specific goals for flood protection or navigation benefits.
  • The “design with nature" approach to dredge design is favored by permitting and granting agencies.
  • The Flood Control Zone 9 Advisory Board has not requested further work on the dredge design.
  • Link to Presentation to Zone 9 Advisory Board on May 23, 2019: https://marinflooddistrict.org/documents/zone-9-advisory-board-meeting-presentation-may-23-2019/
• An analysis of sea level rise and conceptual adaption measures in the Corte Madera Baylands, conducted by the San Francisco Bay Conservation and Development Commission (BCDC) in partnership with the County of Marin and others.
  • Link to report: https://www.adaptingtorisingtides.org/wp-content/uploads/2015/04/Corte-Madera-Baylands-Conceptual-Sea-Level-Rise-Adaptation-Strategy-Report-low.pdf

Timeline

• Assessment of Levee: 2018-2019
• Conceptual Geomorphic Dredge: 2019
• Corte Madera Baylands sea level rise report: 2013

Funding

• The hydraulic and geotechnical assessment was funded by a Local Levee Assistance Program (LLAP) grant from the California Department of Water Resources.
• The concept-level geomorphic dredge design cost $78,000 and was funded by Flood Control Zone 9.
• The Corte Madera Baylands Conceptual Sea Level Rise Adaptation Strategy report was funded by BCDC and its partners.

Zone

Zone 9: Ross Valley

• Marin County Flood Control & Water Conservation District
• California Department of Water Resources
• City of Larkspur
• Unincorporated areas of Marin County