Retrofitting flood control systems could help beaches

FOUNTAIN VALLEY, Calif. — Scientists watch beaches erode, and as cities, state and other entities search for potential ways to help fill the disappearing sand to protect shorelines, a researcher from the University of California, Irvine, said help could lie in flood control systems.

What do you want to know

  • The researcher said that while the flood control system helps keep people and places safe, it has the unintended consequence of minimizing the flow of sediment
  • According to Sanders, they built flood control systems in Southern California in response to severe flooding in the 1860s and again in the 1930s.
  • OC Public Works manages approximately 27 miles of the Santa Ana River
  • Using sediment diversion technology could allow more sediment to flow through flood control systems with the use of nature to push it to beaches

Brett Sanders, a UCI civil and environmental engineering professor, walked along a flood control channel in Fountain Valley and picked up a handful of gritty material piled on the side where the water is flowing.

“Look at that. It’s a really nice sandy material. It’s the kind of material that would be really nice on a beach,” he said.

Sanders said the sediment could be used on beaches with eroding shorelines, such as the stretch of sand north of San Clemente. Instead, the sand is stuck along the concrete that makes up the Santa Ana River, an unintended consequence of a flood control channel, according to Sanders.

“We are seeing a reduction in the delivery of sand to the coast. At the same time, we are seeing an increase in the rate at which sand is washed away by coastal waters. And that’s bad news for beaches,” he said.

He said flood channels like the Santa Ana River were built in response to some historic storms.

“Southern California had severe flooding in the 1860s and again in the 1930s. You couldn’t develop the area, you couldn’t grow and save money if the economy was going to be wiped out by a flood every 30 or 40 years,” he said.

Orange County Public Works manages approximately 27 miles of the Santa Ana River.

Maintenance Inspector Ryan Kolakowski recently checked some sections of the Santa Ana for sediment buildup, like the one that had accumulated near Slater Avenue in Fountain Valley.

“We removed all the sand and sediment from last April and May (2021). So these are all fresh deposits, deposited from this storm season,” Kolakowski said.

Kolakowski took photos of the sediment to coordinate the upcoming cleanup for the 2022 storm season.

Every year, Orange County Public Works crews bring in equipment to pick up the sediment and send it to a sorting site called Miller Basin in Anaheim. At Miller Basin, foreign objects, such as a random part of a walker, are removed.

He said once the sediment is sorted, some of the sand is used for construction projects and some ends up going to the beaches of Newport Beach, San Clemente and Huntington Beach.

“The sand and sediment that you see here, if we didn’t remove it every storm season, it would continue to accumulate. It would basically continue to grow,” Kolakowski said.

He said the structure was built to keep people and places safe.

Sanders said there could be another way of doing things that would be less labor intensive while helping beaches disappear.

“So at the moment our dams are not designed to allow sediment to pass. They don’t have what we call a sediment diversion,” he said.

Such technology could be used at the Prado dam, but he said it would cost money to retrofit existing infrastructure.

“When we have a storm and the water is flowing here at high speed, we want to take advantage of that water so that it not only moves water, but also moves sand towards the beach” , Sanders said.

While the researcher said the flood control channel is amazing and impressive for the engineering it took to build such a structure, he believes there has to be a better way of doing things that takes into account both flood safety and sediment runoff.


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