12/19/2012: Hurricane Sandy – Lessons for San Francisco Bay
December 19, 2012
In a photo from the Jersey shore in the aftermath of Hurricane Sandy, a man shovels a six-inch layer of sand out the door of the kitchen in his beachfront home. Like so many affected by the storm surges of Sandy, I imagine this homeowner is hoping nothing like this ever happens again in his lifetime.
But it almost certainly will. And most scientists agree that as a result of ice melt and thermal expansion of the oceans caused by global warming, rising sea levels will be a root cause of the devastation.
Over the past few decades, damage caused by storms to coastal development has increased both in frequency and magnitude. Homes built on bluffs above the Pacific in cities south of San Francisco are tumbling into the surf, and sea level at the Golden Gate has increased by almost eight inches since 1900. So, while it may be unclear whether or not a storm in 2012 is more severe than a storm in 1912, it is absolutely clear that the same storm in 2012 does more damage to the shoreline because it arrives on higher tides. With higher sea levels, the water cuts more deeply into coastal property and with greater force.
2,000-acre Petaluma Marsh is the largest remnant of a San Francisco Bay tidal marsh complex that once covered 196,000 acres.
Atlantic City, Breezy Point, Staten and Fire Island are among areas hardest hit by Hurricane Sandy. All are located on barrier islands or beachfronts. Barrier islands form when surging seas reach the shallow edge of the continental shelf. Sand is thrust toward the shore from deeper ocean waters, resulting in the formation of linear, sandy islands that parallel the coastline. Look closely at any map of the Atlantic coast and you’ll see a chain of barrier islands that stretches from Long Island to Florida. Left undeveloped, these barrier islands act as natural breakwaters that protect the mainland by capturing storm-deposited sand and reducing the size and power of storm surge.
In a recent New York Times article about barrier islands and Hurricane Sandy’s impact on Fire Island in particular, Henry Fountain wrote:
Fire Island is estimated to have moved 65–85 feet toward the mainland during Hurricane Sandy. Storms across the globe are reconfiguring continental shorelines, reflecting the new reality of higher sea levels. Over time, barrier islands will migrate toward the mainland and grow vertically as sand is moved and redeposited during storms. Because sea levels continue to rise, we can expect to experience more coastal destruction in the future from all storms, big and small.
Barrier islands can be a great place to plant an umbrella and picnic basket on a warm summer day. They are not so good for year-round living on a warming planet. In San Francisco Bay, our tidal marshes function as barrier islands. Like Atlantic barrier islands, San Francisco Bay's tidal marshes are recalibrating in response to sea level rise. If we are to benefit from the protection that healthy tidal marshes offer against sea level rise, we must accelerate their restoration. The longer we wait, the greater the damage will be to shoreline development with each winter storm.