SLO wants to prevent destructive flooding from San Luis Creek. Will it work?
Framed by a thicket of trees and shrubs, the San Luis Obispo Creek flowed gently over rocks and fallen logs on Wednesday morning.
A soiled cloth hanging from the rafters of the Marsh Street Bridge served as the only reminder of last winter, when floodwaters spilled out of the creek and sliced through nearby homes and businesses on Jan. 9, 2023.
That winter, Erik Poor watched the floodwaters slosh out of the creek and destroy his truck and a C-Train full of electrical equipment outside of his Higuera Street business, PoorBoy Electric and Lighting.
“It was gnarly,” he said.
This winter, the city will start construction on a $13 million project to increase the creek’s capacity and prevent future similar events along Higuera Street from Madonna Road to Marsh Street.
“There will continue to be storms in the future, 2023 was not a one-off,” city engineer Noah Maidrand said. “The city is excited to make the investment here, now, to prevent flooding in the future.”
This is the largest flood prevention project the city has ever embarked on, he said.
When the project is finally completed, the creek will be able to hold 40% more water during a severe flood, he said.
Though planning for the project started in 2003 with the formation of the San Luis Obispo Creek Waterway Management Program, the city couldn’t start construction until it secured numerous state and federal permits to remove vegetation and widen the creek.
In the meantime, however, numerous homes and businesses along that stretch flooded in the onslaught of rain the region received in early 2023 — and Poor blamed the city for some of that damage, saying it should have removed vegetation and debris that plugged the river during the storm ahead of time.
Now Poor is glad the city proposed the project — but it’s long overdue, he said.
“If they’re going to do it, awesome,” Poor said. “It’s about time.”
SLO to replace Bianchi Bridge, increase creek flood capacity
Before San Luis Obispo was developed, water meandered gently down a shallow San Luis Obispo Creek. When a storm hit, the creek widened to hold the extra water, then it shrunk again when the rainy season ended.
Over time, buildings and bridges built along the creek squeezed the waterway, while Arroyo Willow trees and invasive plants further choked the creek. With no room to widen, the creek sliced deeper and the water flowed faster — setting the stage for more severe flooding.
As part of this project, the city will widen the river and increase the amount of water it can hold.
“This is an area of San Luis Creek that historically receives a lot of flooding because it’s been encroached on and incised over time, so by widening it out in certain portions and installing bypass channels, we get to increase that capacity,” Maidrand said.
The city will demolish a building belonging to Scott’s Shop on Higuera Street near the Marsh Street bridge to give the creek more space.
“It’s one of the most constricted points of the creek,” Maidrand said.
The city will also remove about 70 trees and shrubs and replace them with healthier, native vegetation, Maidrand said. Invasive plants on the chopping block include castor bean, cape ivy, giant reed and Himalayan blackberry, he said.
The city will then plant more than 300 native trees and shrubs beside the creek. The oak and sycamore trees will provide more shade over the river than existing vegetation, which supports steelhead trout swimming in the water, he said.
Additionally, the city will carve two, 20-foot-long bypass channels able to catch rising water before the creek overflows.
“Once the flood waters reach a certain level, flood waters can flow there rather than over the sides of the creek,” Maidrand said.
One bypass channel will stretch along Brooke Street from the dead end of South Street to the Madonna Road onramp for Highway 101. The other channel will start at Bianchi Lane and extend along South Higuera Street beside Highway 101. Both channels will run parallel to the creek.
Meanwhile, the city will replace the century-old Bianchi Bridge at the end of Bianchi Lane.
In 2006, Caltrans evaluated the bridge for the National Register of Historic Places, but it was found ineligible, Maidrand said.
The new bridge will be 120 feet long with a higher bottom elevation to allow more water to flow underneath.
SLO business owner worried flood prevention plan won’t be enough
Several business owners and workers who spoke with The Tribune said they felt the issue causing the flooding was a lack of regular vegetation management in the area.
On Jan. 9, 2023, San Luis Obispo Creek belched about two feet of water into Scott’s Auto Shop, damaging equipment and leaving a thick layer of mud on the floor.
“It was just a raging river that rushed through the whole shop, it caused a lot of damage,” shop employee Eric Masingale said. “It was horrific, I’d never seen anything like that.”
Shop owner Scott Hayes blamed the city for the flood. He said the city should have removed vegetation in the creek that plugged Marsh Street Bridge during the storm.
“This flood over here would have never happened had the city done their job,” Hayes said.
Hayes said the city’s new flood prevention project will only work if it simultaneously improves their annual vegetation maintenance in the creek.
“I hope that they still maintain the creek because the non-native trees will grow voluntarily and it will clog up the creek,” Hayes said. “This will happen again.”
New flood prevention plan allows live tree removal
The January 2023 flood was partly caused by trees that had grown around the Marsh Street Bridge, constricting the waterway and reducing the creek’s ability to hold water, city biologist Freddy Otte told The Tribune.
The city annually removes downed trees and other obstructions from the creek before winter, but it hadn’t previously been able to remove the live trees growing near the bridge without first getting the necessary state and federal permits.
As part of the new flood-prevention project, the city was just recently able to secure the permits to remove live vegetation, as well as widen the creek, from the Central Coast Regional Water Quality Board, the California Department of Fish and Wildlife, the Army Corps of Engineers and the National Marine Fisheries Service.
“We’ve been working for a couple of years on just securing permits for this project, that’s one of the major hold ups,” Otte said.
He added: “Finally seeing this project come to fruition, it’s a testament to our dedication.”
