By next year work should be underway on National Park Service property at Stinson Beach to gird against rising seas that are predicted to swallow part of Marin’s coast sometime this century.
The threat of sea-level rise is the primary reason why the park service is planning a $2.3 million revamp of a wastewater treatment system that serves more than 1 million people annually at various facilities along the beach and adjacent areas.
Sometime over the next century, huge shoreline swaths of Marin, including Hamilton Field, Highway 37, Highway 1 in West Marin and the Tamalpais Valley could be under water if global warming causes the bay and ocean to rise by a meter — more than 3 feet, according to the San Francisco Bay Conservation and Development Commission, which monitors shoreline development.
That rise, along with sporadic storm surges, will likely send water inland and inundate coastal homes, schools and utilities, including septic systems that serve Stinson Beach rest rooms, among other buildings.
“We want to be proactive, not reactive,” said Chris Carpenter, civil engineer with the Golden Gate National Recreation Area, who is working on the project. “The bigger picture shows several facilities starting to be under water. We know it’s happening and coming. We need to plan to move them away from water and more inland.”
And that’s where the septic system will be relocated, closer to Highway 1, away from the surf. Work could be completed by late 2016.
County prepares
Marin County is working on the sea-level rise issue too.
It has initiated C-SMART: Collaborating on Sea-Level: Marin Adaptation Response Team. The program, overseen by the Marin County Community Development Agency, is trying to get ahead of rising seas.
“Water lines, people’s homes, certain schools, roads, people who have limited mobility, they all will be affected by sea-level rise,” said Jack Liebster, who is heading the project for the county. “We are looking at different categories.”
The team is developing a report on sea-level rise planning for West Marin’s coast, which was discussed at the Board of Supervisors meeting Tuesday and can be viewed at marinslr.org.
“This is very much a collaborative process and we want to hear from the public as we go,” Liebster said.
At the supervisors meeting he outlined efforts to identify what effect climate change will have. Seas have risen 8 inches at the Golden Gate in the past century, but the rise will accelerate in the decades ahead, he said.
Property rights
The California Ocean Protection Council provided a $200,000 grant and the state Coastal Commission $50,000 to the county to look at how it can prevent businesses, homes and highways from being inundated by rising seas.
The supervisors allocated $250,000 for an additional overall “countywide assessment” of sea level rise as well.
Supervisor Steve Kinsey noted “legal research” may be in order in additional to planning review, because climate change issues may “bump up” against property rights of those near the shore.
Marin’s coastal lagoons, wetlands and beaches — including southern Tomales Bay, Drakes Estero, Bolinas Lagoon and Stinson Beach — could be at risk of drowning over time unless action is taken to increase their resilience.
Highway 1 could be inundated at many different locations, with about 6 miles affected, cutting off large areas of the coast. Homes in places like Stinson Beach’s Seadrift also could face issues with sea-level rise, according to the county.
Inland, San Francisco Bay Conservation and Development Commission maps show the bay pushing almost all the way to Highway 101 in parts of Novato, as well as water covering low-lying areas of Mill Valley, Sausalito and Tiburon, among other areas.
“Right now we are looking at the coast but we want to begin to talk to the cities on the bay side and have them work with the county on the issue,” Liebster said.
IJ reporter Nels Johnson contributed to this report.
