Arroyo Grande Creek breached levee, flooded farms. How will SLO County prevent more damage?

While a severe rainstorm battered San Luis Obispo County on Jan. 9, the Arroyo Grande Creek breached the south side of its levee and flooded nearby homes and farmland in Oceano.

Nearby residents were forced to evacuate.

To protect the area from future flooding, the San Luis Obispo County Public Works Department has kicked off a project to remove excess sediment from the creek, restore its flow capacity, and repair the levee to match its conditions prior to the winter storm series.

“I know that the impacts of last winter were felt wide and far within the community,” county Public Works Department deputy director Kate Ballantyne said at a news conference on Wednesday announcing the project. “We really appreciate everyone working with us, and again, their patience while we get through this project.”

Restoring the creek will cost about $1.8 million, but repairing the levee will cost even more, according to project manager Brandon Zuniga.

The Federal Emergency Management Agency’s Public Assistance Program should reimburse the county for 75% of the project’s costs, while the California Governor’s Office of Emergency Services is expected to reimburse the other 25%, Zuniga said.

The project will be completed in two phases on the south side of the levee in Oceano.

How does SLO County plan to restore creek?

For the first phase of the project, the county will remove 11,000 cubic yards of sediment from the creek, Ballantyne said.

The county will also clear vegetation in the creek “to allow for clear pathways for the flow of water,” she said, while preserving some vegetation for wildlife habitat.

That work started on Sept. 11 and should be completed by the end of October depending on weather conditions, Zuniga said.

During phase two of the project, the county will conduct $500,000 of erosion repairs on the levee, according to Ballantyne.

The county will then build a hydraulic barrier around vulnerable sections of the structure.

The county has not yet received bids for construction of the barrier, “but I anticipate that will be in the millions-of-dollars range,” Ballantyne said.

As of Thursday evening, it wasn’t clear when phase two would be complete.

“The county is the lead agency responsible for the maintenance of the channel here,” she said, but collaborates with numerous regional, state and federal agencies to take care of the area.

California State Parks, the Federal Emergency Management Agency and the California Governor’s Office of Emergency Services worked with SLO County and the Arroyo Grande Creek restoration project.

Construction is being partly funded by a $1.2 million allocation from the state secured by state Senator John Laird and California State Assembly Member Dawn Addis, who both represent parts of San Luis Obispo County in the State Legislature.

“It was such an intense moment of the community and government coming together,” Addis said. “The speed with which they have gotten to work on this project is really tremendous.”

Will Arroyo Grande Creek levee hold during winter rains?

Meteorologists are predicting El Niño weather patterns for the West Coast this winter, which means San Luis Obispo County could be doused with another season of above-average rainfall.

“The work we’re doing now is more important than ever,” San Luis Obispo County Supervisor Jimmy Paulding said during Wednesday’s news conference. “While a much bigger project and longer term solution is needed, it is my hope that these projects will minimize flooding impacts in Oceano this winter.”

Filled with rainwater from winter storms, Lopez Lake spilled for the first time in 25 years in March.

Now, the reservoir is 96% full — and threatening to flood into Arroyo Grande Creek next time the county receives heavy rain, Ballantyne told The Tribune after the news conference.

“We expect the lake to fill and spill early in the season,” she told the Tribune. “We’re keeping a very close eye on that.”

As climate change progresses, severe storms could become common on the Central Coast, stressing infrastructure built with milder weather patterns in mind, Laird said.

“The infrastructure in the state was designed in a previous climate,” Laird said. “Now we’re moving to a different climate and having to dramatically adjust.”

Laird said that restoring the creek and repairing the levee will be insurance against future “wild swings” in weather patterns.

How can county support farmland, housing in a floodplain?

The entire farming area south of the levee is in a floodplain, according to the Federal Emergency Management Agency.

The levee repairs should hold for 10 to 20 years, according to Ballantyne, but the county is looking for ways to protect folks living and working in the floodplain for longer.

This could look like using grant funding to expand the creek’s channel capacity or “removing people from vulnerable positions in the floodplain,” Ballantyne said.

Other San Luis Obispo County communities are also grappling with the challenge of being built in floodplains.

In Morro Bay, a mobile home park and numerous businesses are located in a floodplain. The community flooded twice during the winter storm series.

Laird advised local agencies to explore Caltrans’ Protect Program, which sets aside grant funding for infrastructure projects that “address vulnerabilities due to weather, natural disasters, and climate change,” its website said.