San Rafael, CA – The Marin County Department of Public Works (DPW) has been awarded a $400,000 Adaptation Planning Grant from the California Department of Transportation (Caltrans). The grant will fund a project to develop conceptual sea level rise adaptation strategies from the intersection of Highways 101 and 1 in Tam Valley and north to Mill Valley.
Shoreline Highway near the Manzanita Park & Ride lot is notorious for flooding, sometimes even when there isn't any rain. The project consists of technical studies followed by community engagement initiatives to adapt to sea level rise for the area. The goal is to develop a better understanding of what measures could be taken to protect southern Marin’s critical transportation corridor in an environmentally sustainable manner, maintaining bicycle, pedestrian, transit and vehicular access.
The estimated cost of the research project is $515,000. The anticipated $115,000 beyond the grant funding will come from local funds through the Transportation Authority of Marin, the Marin County General Fund and the Marin County Flood Control Zone 3 budget.
The Tam Valley region, particularly around the highway on/off ramps and the Manzanita Park & Ride, has been inundated by flooding for years, causing problems for local and commuter traffic as well as public transit. The flood events, while usually associated with storms, can even occur on sunny days during high tides. Long term settlement of the underlying bay mud, together with sea level rise has already exacerbated these issues and is expected to increase in the future, as detailed in the Marin Shoreline Sea Level Rise Vulnerability Assessment, released June 2017.
In addition to developing strategies and concepts to improve transportation and resilience to tidal and storm flooding, the study will coordinate and partner with Marin County Parks to develop nature-based projects that improve the resiliency of the 106-acre Bothin Marsh Open Space Preserve to sea level rise. Future projects would include evaluating the southern section of the Mill Valley-Sausalito Multiuse Pathway, a popular nonmotorized commuter and recreational route that traverses Bothin Marsh, which had a series of improvements made to its northern stretch during 2017.
The newly awarded Caltrans grant provides an opportunity to incorporate transportation (vehicular, bicycle, pedestrian, and transit) improvements with nature-based adaptation strategies to evaluate wider-reaching, holistic options that include improving natural wetland functions for southern Marin. While costs of future infrastructure projects are unknown, the results of the upcoming research project will enable stakeholders and community members to discuss the full scope of risks, benefits and feasibility of potential adaptation options.