by Tony Soprano » Sun Aug 04, 2013 9:26 am
Statement of the SFBA
I agree that this is a problem, but of very substantial scale. My background is in coastal engineering and shoreline retreat on the open coast. The beaches on the West Bay in this area are highly disturbed, and the shoreline is both retreating and adjusting, as well as responding to sea level rise. There was a pretty good look done at Coyote Point as part of the County's efforts to build a beach there. Essentially, the shoreline was pushed out with fill over the mudflats. (It is also altered by other nearby fill areas, like that to the up coast of the power lines.) All of this alters both the supply of sand and the wave energy. David Lyon has poked around a bit, and I asked two technical experts--Bob Battalio, ESA's coastal engineer, and Peter Baye, who has worked on beach restoration (e.g Aramburu Island in Marin County) for a little informal help.
There are two problems. First, long term erosion and sea level rise has eroded not just the beach, but areas up wind (up wave energy direction), so shoaling of waves occurs closer to the beach, bringing more wave energy and accelerating erosion. Second, but not so clear to me, the shoreline was perhaps filled many years ago and is now seeking a new equilibrium. Unless we understand the issues, and have the City behind us, any restoration efforts are doomed.
The good news is that the agencies who regulate the shoreline now understand that soft solutions--eg. restored beaches--are better habitat than rip-rap. So there are some prospects for eventual support and solutions, but the price tag is in the millions, and the time scale is in the five to ten year horizon.
Sorry to not have better news.
Jim McGrath
Vice President San Francisco Board Sailing Association
Board Member San Francisco bay conservation and development commission