Sand replacement ‘pretty successful so far’

Sand replacement ‘pretty successful so far’
According to a consultant’s report presented to Solana Beach City Council members June 8, city beaches “are looking pretty good right now.” Photo by Bianca Kaplanek

SOLANA BEACH — The city’s beaches “are looking pretty good right now,” thanks in large part to two major sand replenishment projects, according to a report presented at the June 8 council meeting.

“I think you guys made out pretty well in both of these projects,” said Greg Hearon from Coastal Frontiers Corp., a consulting firm that provides specialized services in coastal engineering, coastal oceanography and hydrographic surveying.

Hearon discussed the results of a 2015 shoreline monitoring program that includes data through fall 2015 and preliminary information gathered since the recent El Niño conditions.

The monitoring program was established in 2002 after the first regional beach sand project, referred to by the consultant as RBSP I, conducted by the San Diego Association of Governments.

The objectives are to measure and document changes in beach width over time, quantify the impacts of the two regional projects and develop a foundation for future projects.

“We essentially collect beach profiles, or cross sections, of the beach … in the fall and spring that correspond with the beginning and end of the winter wave season,” Hearon said.

It has been two years since Solana Beach received an update.

Since 1994 almost 6 million cubic yards of sand have been placed on beaches in what is called the Oceanside cell, which runs from that city south to La Jolla.

Data is collected in Solana Beach at four locations, including Fletcher Cove, Tide Park and two sites in the south end of the city.

The consultants analyzed data from last year; after RBSP I from 2000 to 2015; after RBSP II from 2011 to 2015; and following the 2015-2016 El Niño.

They looked at beach width and shore-zone volume, or the amount of sand from the back of the beach out to the depth of closure where waves and currents aren’t really moving sand around very much anymore, Hearon said.

Last year there were region-wide beach width gains but stable or diminishing shore-zone volumes, which seem “somewhat contradictory,” Hearon said.

After inspecting the profiles it looked like the sand in the near-shore bars moved up to the above-water beach in greater quantities than it typically does in a summer season, he noted, adding that a similar outcome occurred 2006.

“We had wave conditions that were particularly conducive to bringing sand from the bars up to the above-water beach,” Hearon said. “And it seems that we’ve had a similar phenomenon this last summer, which is nice going into an El Niño winter (because) we had a lot of sand on the beach to act as a buffer.”

Since RBSP II was completed in 2012 there have been gains at the receiver sites, including Solana Beach. But many sites lost the sand fairly quickly at the beginning as it started to disperse and fill adjacent beaches, Hearon said.

There’s been criticism recently because the assessment was only looking at erosion at the receiver sites and not considering the benefits to adjacent beaches.

“We feel it’s more appropriate to look at it on a regional basis or break it up into sub-reaches” such Oceanside, north Carlsbad, Encinitas and Solana Beach, Hearon said.

According to that analysis the consultants found shoreline advancement in all of the nine sub-reaches and shore-zone volume gains in six.

“So I think it shows that the program’s been pretty successful so far,” he said.

Since RBSP II the beaches in Solana Beach are about 54 feet wider, with an improved performance compared to the first project, Hearon said. City beaches to the south have also benefitted.

Hearon said the results of the second project are likely better because the sand used was much coarser, “so it’s hung around longer.”

Compared to post-RBSP I the beaches are about 82 feet wider, showing an 80 percent gain, he added.

According to preliminary findings following the recent El Niño, Solana Beach fared well this past winter, especially compared to previous El Niño conditions in the late 1990s and 2010.

In fact the severity of erosion was the lowest when compared to all cities in the Oceanside cell.

“It’s a nice outcome for you,” Hearon said, noting that beaches were better prepared for the recent El Niño in part because of previous sand replenishment projects.

But there is currently a deficit of nourishment.

“We’re putting on about 200,000 cubic yards per year less now than we were about 15 or 20 years ago,” he said. “So if we want to keep the beaches in the state that they’re in now that’s something that the region’s going to have to look at and address to find ways to get sand on the beach.”

“It’s really good to see (this information) because we definitely get some questions from residents at times wondering if it’s worth (spending) all this money to put sand on the beaches because it just washes away,” Mayor Dave Zito said.

“And this shows that the benefit is actually quite long term for us,” he added.

0 Comments

Leave a reply

Your email address will not be published. Required fields are marked *

*

or

Log in with your credentials

or    

Forgot your details?