The geography of the watershed, in which rainfall channels its way from the surrounding hills down through Marin City and out to Richardson Bay, creates complex challenges for developing flood risk reduction measures. The densely populated area was built upon wetlands before contemporary construction methods and stormwater runoff can overwhelm the neighborhood’s aging drainage system and lead to localized flooding, particularly when storms and high tides coincide.
To successfully design and implement any long-term flood mitigation efforts that consider future sea level rise projections, it is crucial to plan for as many variables as can be identified. Past studies have identified elements that need to be addressed in the current Stormwater Plan’s process, as well as the critical involvement of Marin City residents and stakeholders, which will enable development of designs that specifically address the concerns and needs voiced by the community.
Additionally, the high cost of potential projects poses a hurdle. The timing of implementing projects hinges heavily on funding availability. The anticipated heightened costs of flood risk reduction projects in this complex watershed means that the County and the District’s funds may require significant state and/or federal funding assistance. State and federal funding sources, such as grants, can take a significant length of time to secure.
The current Stormwater Plan aims to reduce the potential timelines for securing grants by building upon evidence and data from previous studies and exploring ways to address historically flood-prone areas, such as the upper watershed and the Drake/Donahue intersection.