SLO realigns part of Prefumo Creek ahead of storm season

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A row of houses sandwiches a chained-off dirt parcel on Vista Del Lago Road, almost obscuring it as someone’s front yard.

Owned by the city of San Luis Obispo, that plot is a pathway to Laguna Lake. On a recent Tuesday evening, it led to a scenic twilit sight. Swatches of the mirror-like lake interspersed with patches of tall grass and bushes, completed with the lit top of the Madonna Christmas tree peeking over the background.

It’s hard to imagine that almost a year ago the lake overtopped and flooded the neighboring Oceanaire Drive streets due to heavy January storms.

The city’s Public Works Department devised a solution to mitigate potential future flooding as the winter storm season approaches. Staff realigned a section of Prefumo Creek that lies to the right of the city’s Vista Del Lago parcel. The creek snakes into Laguna Lake but Prefumo’s last 500 to 1,000 feet make sinuous 90-degree turns that reduce water-carrying capacity, according to supervising civil engineer Wyatt Banker-Hix.

“In order to increase the amount of water, we want the creek to be able to carry during the storm event and minimize the chance that debris gets lodged in the creek and backs up the entire creek, what we’ve chosen to do is realign it,” he said. “That just means dig a new primary channel.”

Banker-Hix told New Times on Dec. 12 that Public Works started deepening and widening Prefumo Creek’s primary channel in October while the realignment project started in November and was completed the week of Dec. 3. Public Works funded both using $1.5 million from the city’s emergency reserves and capital projects budget. That money stretched to cover excavation and repair of a culvert.

“During the March storms, a series of culverts drained into this section of Prefumo Creek,” Banker-Hix said. “All those storm drains were backed up so there was localized intersection flooding.”

Now, the small portion of the old primary channel of Prefumo Creek will serve as a secondary overflow channel. Banker-Hix pointed out the new realignment as he walked on a long stretch of muddy creek bank grooved with tire tracks.

“This whole section of channel was open water. This was dredged, there was no creek, and this was just a portion of Laguna Lake,” he said. “Everything we’re standing on right now is accumulated sediment … that’s all been accumulated since the 1960s when this creek was rerouted and Laguna Lake was dredged.”

He added that Public Works chose the section of Prefumo Creek near Vista Del Lago for realignment because it’s a repeat offender when it comes to debris, sediment, and vegetation accumulation and is an area that needs frequent maintenance.

“We recognize this was a portion holding the rest of the creek up,” Banker-Hix said. “We knew that if we had a couple more big storms and saw 2 to 4 feet of sediment being deposited, we’d soon be in a place where this would be perennially flooding.”

Usually, Public Works is authorized to remove up to 2,000 cubic yards of debris, but the Prefumo Creek realignment project ended up removing five times as much. The work also resulted in a flood bench and an emergency access road that will allow people and equipment to move through for future debris management.

“The new creek is much more straight and actually exits into the deepest section of Laguna Lake,” Banker-Hix said. “[The old creek] ended up ping-ponging and threatening private properties. It would swing from a property on the Oceanaire side and then to a property on the Vista Lago side. That slows down the water, and a lot of debris can accumulate there. It would be very difficult for us to enter and clear the debris.” Δ

This article appears in Last-Minute Gift Guide 2023.