Photo by Bryan Archbold
Photo: The cobblestone-covered Ash Avenue beach finds Tom Truax foraging for garden rocks. According to Carpinteria Parks and Recreation director Matt Roberts, massive tides, a major contributor to beach erosion, wipe clean the sand from Carpinteria’s shores, exposing the bed of rocks found underneath.

City looks to halt erosion of Carpinteria’s beaches
“The World’s Safest Beach” is in danger of becoming the world’s smallest beach.

Though the gradual erosion of one of Carpinteria’s greatest assets might not be a concern to the average beachgoer soaking up the sun, it has become an increasing problem along the Central Coast that city officials, in conjunction with several government agencies, are looking to rectify through a number of preventive measures.

“There’s just not as much sand in the system as there was 50 years or 100 years ago,” said Patrick Barnard, a coastal geologist with the United States Geological Service (USGS).

Barnard, who, with the USGS, U.S. Army Corps of Engineers and the city, all in the process of carrying out shoreline studies to devise a solution to the problem, said that erosion can be caused by a number of factors. Some natural, some man-made, they range from beachside development disrupting shore structure; the effects of global warming; and changing seasonal tides leading to a depletion of beach sand supply.

In the latter situation, explained Barnard, sand migrated onshore from spring tides is later pushed back out to sea from stronger waves in the winter. Over time, this can cause some shore sediment to be lost.

“Through time, you can start to see a certain amount of that sand isn’t making it back,” he said. “If there’s not enough sand coming out to the west or coming in to the east, you’re going to have erosion.”

According to Jim Bailard, a technical advisor for BEACON, the Beach Erosion Authority for Clean Oceans and Nourishment, erosion in Carpinteria can be traced back to the 1930s, when Rock Beach on Santa Claus Lane incurred up to 500 feet of shoreline loss when construction of the Santa Barbara Harbor blocked off sand flow.

“That was the most extreme example,” he said. “When you block it off, you end up starving downcoast beaches.”

Since then, continued Bailard, simple geography has been one of the main reasons for Carpinteria’s erosion, with Ash Avenue’s beach hit hardest. According to Barnard, since longshore current flow runs in an east-west direction, westernmost Carpinteria shores tend to erode more.

“One of the reasons there’s erosion in Carpinteria is because sand is being collected on the Montecito side,” he said.

According to information gathered from Web site surfirder.org, approximately 950 miles of California’s 1,120 miles of coastline are actively eroding.

In the first of a few scheduled surveys, the USGS, noted Barnard, came to the city in October 2005. The geological studies, he said, include mapping a three-dimensional picture of the shore through usage of an all-terrain vehicle equipped with a GPS tracking system. Out in the water, bathometric studies including jet skis with a global positioning system (GPS) and echo sounders have been used. Their purpose, he noted, is to measure, by volume, the amount of sand being eroded away and the most suitable solution to preventing the problem.

One of those solutions, according to Carpinteria Parks and Recreation Department director Matt Roberts, is the construction of a “soft structure,” a reef-like submerged breakwater to buffer the amount of sand lost out to sea. Roberts believes the endeavor could be more feasible than erecting a solid seawall of concrete or rocks and may help promote the growth of more ocean-dwelling life.

“In my own view, it will help grow a bigger kelp bed,” said Roberts.

Another possibility is the process of “beach renourishment,” replacing sand each season lost to erosion with near-shore sand, according to Roberts.

Roberts said $2.2 million has been allocated for the studies, split equally from federal and state funding. The recent involvement of the USGS, he added, incorporates $160,000 of that cost. The next round of beach studies, he noted, will be conducted in March.