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Vice chair presents sea-level rise and subsidence update showing subsidence currently outpacing sea-level rise in Mariner Cove
Summary
Vice Chair Ken Bongren summarized local datasets and projections showing subsidence in Mariner Cove (about 10 mm/year) currently contributes more to relative sea-level change than ocean rise; combined sea-level rise and settlement could expose low spots to multiple feet of water in major storms by midcentury.
Ken Bongren, vice chair of the Corte Madera Flood Control Board, presented a data update for Mariner Cove that combined historic surveys, satellite measurements and state sea-level guidance to show how land subsidence and tides together affect local flood risk.
Bongren said his analysis used three main local sources: the AN West subsidence study (2007), recent satellite-based measurements summarized in a 2024 Science article, and the town’s updated Storm Drain Master Plan prepared by Schaff & Wheeler. “I wanted to have a common understanding for members of the flood board and the town and the community to understand what the historic land surface and sea level has been, what it is now, and what it’s predicted to be in the future,” he said.
Key findings presented: - Measured subsidence: Recent…
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