The future of the increasingly worn section of coast known as Surfer's Beach will be the subject of a public meeting Monday. The U.S. Army Corps of Engineers, in partnership with San Mateo County Harbor District, will present baseline conditions as part of a larger effort to combat erosion at the El Granada beach.
"(In) understanding how the waves and tides and currents interact with each other, we'll have a better understanding of the site, and we'll better know how to reduce the erosion rates," said the Army Corps Coastal Engineer Lisa Andes. "It's really important to understand the site, before we start talking about solutions. The first step is defining the problem. And to do that we look at the tides and the waves and the current."
In the early 1960s, the Army Corps built the outer breakwater to form the harbor. The structure changed the area's wave patterns and, as a result, accelerated coastal erosion at Surfer's Beach. The eroded beach eats away at the Highway 1 embankment and detracts from recreational uses at the beach. The damage also threatens the western snowy plover - a small shorebird listed as threatened under the Endangered Species Act.
Various agencies and individuals have offered up possibilities for the erosion problem. Those ideas include building an artificial reef, poking a hole in the breakwater to see if circulation could be restored, and building a small structure to trap sand and haul it away. Dredging is another option. To do that, harbor sediment would be transferred to Surfer's Beach. It's unclear, however, if the sand would stick to the beach over time.
Before anyone can come up with a successful approach, the Army Corps of Engineers must conduct a study that takes into account all the factors that erode Surfer's Beach. To kick the $1.2 million study phase into gear, the engineers must establish the baseline condition of the eroding beach.
To accomplish this, the engineers collaborated with the U.S. Geological Survey to disperse tide gauges and buoys to collect information about wind, waves and water. By studying the patterns of how sediment moves in waves, tides and currents, the engineers can begin to understand how to solve the problem, according to Andes.
Andes expects mixed baseline conditions because there tends to be more sediment during the winter and less in the summer. She said her team has picked representative summer and winter month conditions, and at the public meeting they will present their estimates of the erosion rates.
Within the next few weeks, the Army Corps of Engineers will remove the field instruments. They will spend the remainder of the summer analyzing the data and calibrating a model of Surfer's Beach that uses waves and tides and wind to estimate sediment transport. Later this year, the engineers will propose alternatives for the beach, which they will introduce to the community.