04/29/2019
Seawalls and other such hard barriers such as the one proposed for the West Trail leading to Mavericks at the north end of Pillar Point Harbor are a bad idea and lead to more problems in the long-term. A radical, synthesized approach that combines managed retreat with a "living shorelines" model would protect the coastline better by combating and planning for erosion more effectively, and would ultimately be cheaper for county taxpayers:
"The study found that along the hard-hit shorelines, three quarters of the bulkheads were damaged by Hurricane Irene. The walls, typically concrete and about two meters high, are the standard homeowner defense against the sea in many parts of the country. Yet none of the natural marsh shorelines were impaired. The marshes, which extended 10 to 40 meters from the shore, had lost no sediment or elevation from Irene. Although the storm initially reduced the density of their vegetation by more than a third, a year later the greenery had bounced back and was as thick as ever in many cases.
"The study confirmed what many experts had begun to suspect. “Armored” shorelines such as bulkheads offer less protection against big storms than people think. By reflecting wave energy instead of dispersing it, they tend to wear away at the base, which causes them to gradually tilt seaward. Although they still function well in typical storms, they often backfire when high storm surges overtop them, causing them to breach or collapse, releasing an entire backyard into the sea.
"In a later study, researchers surveyed 689 waterfront owners and found that the 37 percent of properties protected by bulkheads had suffered 93 percent of the damage. And bulkhead owners routinely had four times the annual maintenance costs of residents who relied on nature instead. Salt marshes bent but did not break.
"In recent years more scientists and policy makers have come to believe that “living shorelines”—natural communities of salt marsh, mangrove, oyster reef, beach and coral reef—can be surprisingly effective in a battle coastal residents have been losing for years."
Fortified wetlands can protect shorelines better than hard structures