California State Route 37 Stewardship Study
The University of California Davis Road Ecology Center undertook a stewardship study to assess the risk to California State Route 37 (SR 37) from sea-level rise. SR 37 passes near San Francisco Bay, connecting Interstate 80 and Highway 101. The road corridor and surrounding wetlands are threatened by sea-level rise and flooding. The road bed sits below sea level at its lowest elevation and is likely to experience erosion, flooding during storms, and inundation due to sea-level rise. The State Road 37 Stewardship Study (Study) included a stakeholder process and technical analyses to determine possible future solutions to reduce the vulnerability of the highway to climate impacts.
The Study team used GIS modeling and valuation of ecosystem services methods to compare possible alternatives for adapting the highway, including: continuing “business as usual” maintenance, armoring and raising the highway on fill, elevating the highway onto a causeway, and two approaches to realigning the highway with other roadways and away from the Bay edge. The Study applied sea-level rise projections of up to 1.5 meters by 2100, based on models developed by the Bay Conservation and Development Commission (BCDC), to assess the vulnerability of the highway to impacts. Five specific alternatives for adapting the corridor were presented to stakeholders and community members for their consideration. The preferred option among both groups was the construction of causeway that elevates the highway at the areas of lowest current elevation.
In addition to the stakeholder and community member surveys conducted by UC Davis, the Study team cited technical analyses that assessed the effect of sea-level rise on particular areas along the SR 37 corridor. The Hayward Shoreline Planning Agency (HASPA) commissioned a report to examine the localized effect of 55 inches of sea-level rise, based on State of California guidance, over the next century on the Hayward Shoreline, located close to the SR 37. That analysis included a catalogue of adaptation options including levees and sea walls, as well as relocation of infrastructure and population.
The SR 37 Stewardship Study was supported by the Transportation Research Board Strategic Highway Research Program 2. The Study involved a collaboration between Caltrans District 4, the UC Davis Road Ecology Center, the Sonoma Ecology Center, Southern Sonoma County Resources Conservation District, Sonoma Land Trust, and Napa County Resources Conservation District. The Study seeks to meet Caltrans’ triple bottom line goals: preserving the environment, supporting a robust economy, and promoting transportation equity. The Study also advocates for a collaborative ecological stewardship approach rather than the conventional project based permit-and-mitigation approach.
The Study was intended to inform corridor planning for SR 37. The Caltrans Corridor Plan for SR 37 was published in draft form in 2010. That Corridor Plan includes an analysis of the risk to the corridor of sea-level rise and flooding due to the impacts of climate change. That analysis projects sea-level rise of 12-18 inches by 2050, based on data from BCDC and the Intergovernmental Panel on Climate Change (IPCC). Caltrans acknowledged that SR 37 would have to be protected from flooding due to sea-level rise in the coming decades. SR 37 is also projected to be made more vulnerable to flooding by the removal of levees as part of the restoration of adjacent wetlands. These wetlands contain endangered species and habitats and are undergoing restoration to restore their natural function.
Building on information from the SR 37 Stewardship Study, Caltrans approved a Transportation Concept Report (TCR) for SR 37 in January 2015. The TCR further evaluates current and projected conditions along SR 37 and lays out a vision for developing and improving the route over a 25-year planning period. The TCR recognizes sea-level rise and flooding from storm events as a critical concern for planning the corridor. The concept plan includes raising the roadway for the segments of SR 37 that are between Highway 101 in Novato and Mare Island in Vallejo. Corridor planning for the SR 37 corridor is ongoing, and a Phase II study (SR 37 Integrated Traffic, Infrastructure and Sea Level Rise Analysis) was completed in February 2016. This second study continues the partnership between Caltrans and UC Davis, and analyzed potential inundation, vulnerability, and risk for SR 37 due to sea-level rise, and evaluated three reconstruction options: a roadway elevated on a levee/embankment, and two different options for a roadway elevated on a causeway (one with a box girder design and one with a concrete slab and pier design). Phase II included inundation mapping, a shoreline and highway vulnerability assessment, conceptual engineering design and cost estimates, and analysis of community and ecosystem benefits; and final reports have been published documenting these steps. Stakeholder meetings were also held quarterly since September 2014 throughout the development of the Phase II study.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on March 31, 2016.
Publication Date: February 2016
- University of California, Davis
- California Department of Transportation (Caltrans)
- Sonoma Ecology Center