Blaise Simpson and Jung Vu from Gate 6 ½ attended the April 14 meeting of the Flood Zone 3 Advisory Board at the Marin County Civic Center. They were the only members of the public present, along with District 3 Supervisor Stephanie Moulton-Peters and her aide, Jennifer Imbimbo.
Here’s her report:
Advisory Board Chairperson, former Mill Valley mayor, and Marin Disaster and Citizen Corps member Garry Lion mentioned the tide discrepancy last January when introducing item A of the District Staff Reports, Lion’s Gate Sea Level Rise Adaptation Concept. His proposed solution to Sea Level Rise for Mill Valley called for a Richardson Bay Tidal Gate.
Lion started with a graph of expected Sea Level Rise in California, showing that the intermediate forecast of SLR would be 3 feet by 2100 and 5.6 feet by 2150. That’s in addition to tides and severe weather events such as the one in January.
The Richardson Bay Tidal Gate would be a partially submerged sea barrier wall with a computer-controlled navigable passage which would utilize the tides’ effects when they are beneficial and lock them out when detrimental. It would be designed to:
- Keep the inner waters below a safe level (sub king tide) at all times.
- Support ecological flushing of the marshes and fish passage.
- Reduce riverine flooding creeks emptying into the Bay during stormy weather.
- Block escalating high tides created by Sea Level Rise.
- Neutralize storm surge during stormy weather.
During the public comment portion of the meeting Jung Vu told the advisory board about his MarinFlood Application that can predict tides during severe weather events with greater accuracy than other tide apps. Based on historical analysis following the January storms, Vu demonstrated that his software predicted tides within inches of their actual levels, rather than the foot and a half discrepancy shown by normal charting.
Lion’s presentation was well thought out and differed from the usual discussion of incremental fixes, such as shoring up berms and repairing pumping stations. Instead Lion went on to demonstrate that a Tidal Gate would not require any new technology, except software to forecast storm run-off and mentioned that Bel Marin Keys uses similar technology from the 1980s. He noted that Inner Richardson Bay is uniquely suited for a Tidal Gate because it is enclosed, with a narrow, shallow entrance. It also has suitable anchor points for the Tidal Gate Wall and he presented three possible locations for the wall. One site, from Starboard Court in Strawberry to Gate 6 ½ Road, would encompass part of the floating homes community.
To me, it was heartening to see that at least one member of the board was thinking of a larger solution to a problem that over time will only become bigger and harder to solve. At the end of Lion’s presentation, I stood up during the public comments to mention a successful example of a similar gate I had seen in New Bedford, Massachusetts.
Built by the Army Corps of Engineers in the 1960s to protect the largest commercial fishing fleet in America, the New Bedford Hurricane Protection Barrier lies across New Bedford and Fairhaven Harbor, approximately 50 miles south of Boston. The project protects about 1,400 acres in New Bedford, Fairhaven and Acushnet from tidal flooding associated with hurricanes and coastal storms. For more than 60 years, the barrier has been extremely successful in protecting billions of dollars worth of ships, shoreline, homes and coastline. More information about it is available at the US Army Corps of Engineers, New England District Website.
The other interesting item on the agenda was in the Staff Report, Item B, regarding the County’s five-year Capital Improvement Program (CPI). Among other projects being budgeted, it showed a second culvert under Highway 101 to be created by Caltrans. At the previous meeting in January we heard District Staff Senior Program Coordinator Tony Swan repeatedly state that he’d heard Gate 6 ½ residents’ concerns about the water coming from the aging Caltrans culvert at the dock entry. A second culvert will help to even out the velocity of water coming at us from the Marin City catchment pond. This is a win for our community and shows the importance of showing up at meetings like this to make our voices heard.