Observations collected by Scripps Institution of Oceanography, UC San Diego, show that San Diego’s beaches are 10-15 meters (33-50 feet) wider than after an average winter. They are up to 25 meters (80 feet) wider than in early 2010 during the last El Niño winter storms, researchers said.
In the case of La Jolla-area beaches, that unusual width was not helped by human intervention though other beaches have had sand pumped from offshore in recent years, said Scripps oceanographer Robert Guza, the beach survey project leader.
“Cardiff, Solana Beach, and Imperial Beach are wide at least partially because they were nourished with sand in fall 2012,” said Guza, “but Torrey Pines was not nourished recently, and the winter beach there is the widest in 10 years.”
High and steep winter waves move sand from near the waterline to an offshore sandbar, narrowing the beach available for recreational use. Gentler summer swell pushes sand back upslope and widens the beach.
Typical beach width differences between summer and winter are 15-25 meters (50-80 feet), said Bonnie Ludka, a graduate student in Guza’s research group.
This winter, which officially ends on March 20, has been unusually mild, according to scientists. Scripps researchers measured the beach width using readings from GPS units mounted on Jet Skis and all-terrain vehicles.
“Wave heights at the Scripps Torrey Pines offshore buoy never exceeded three meters (10 feet) and only topped two meters (seven feet) for about 40 hours, compared with 190 hours in an average winter,” said Scripps graduate student and survey member Sean Crosby. “The few high waves that did occur coincided with lower-range neap tides, minimizing shoreline erosion.”
Fewer and less intense storms also continued the Southern California drought now entering its fourth year.
“In the coming decades, accelerated sea-level rise is expected to force overall beach retreat on top of the seasonal fluctuations,” said Scripps oceanographer Reinhard Flick.
The California Department of Parks and Recreation, Division of Boating and Waterways, and the US Army Corps of Engineers sponsor the Scripps beach and wave measurement programs.
– Robert Monroe