Supervisors examine historical flooding north of Chico
They descended Tuesday (Feb. 11) on the Butte County Board of Supervisors chambers.
One after another, residents in the flood-prone neighborhoods just north of Chico’s city limits addressed the panel, lamenting longtime inaction to mitigate the flood risk in the unincorporated region, pleading for the supervisors to place a moratorium on new development in the Rock Creek and Keefer Slough drainage basin, and raising concerns of elevated nitrate levels in well water.
The residents expressed their complaints against the backdrop of storms in February 2019 that flooded properties, threatened others and led to an evacuation warning for the community of Nord. Homeowners have been anticipating similar flooding going forward and say the problem goes back decades. So far, solutions have proved elusive.
Steve Schuster, who has lived in the Rock Creek and Keefer Slough area for about 25 years and developed the Sierra Moon subdivision, told the board that a lack of maintenance—regularly clearing out the channels of vegetation and debris—has led to rising levels in the slough over the last 20 years.
The main problem, he said, is the bifurcation of local channels, Rock Creek and Keefer Slough west of where Keefer Road meets Cohasset Road. Schuster said he owned the property at that diversion point between 1991-2002. Traditionally, he said, 70 percent of water flows down the creek, while 30 percent flows down the slough.
During the storms last February, Schuster estimated that 90 percent of the water was diverted into the slough, an unsustainable amount that led to overflow, flooding homes, roadways and orchards. That led to the county proclaiming a local emergency.
Schuster noted that after a major storm in the late 1990s, he allowed county workers on his property to clear out the channel and restore historical creek and slough levels.
“As far as I know, they’ve never been back—until last year when everything went to hell,” Schuster said. “So, it’s crisis management in that creek, and that’s what’s causing the problem.”
Paul Behr, chairman of the Rock Creek Reclamation District, a flood management and groundwater sustainability district, told the panel the district has spent more than $100,000 clearing Rock Creek over the years, and work continues to help keep it flowing unencumbered. He noted, however, that the creek can handle only so much water before levees are breached. Such a scenario threatened to play out in the ’90s, when water overflowed and evacuees in the Nord community escaped with children on their shoulders.
“The problem is, we’ve got 2 gallons of water going into a 1 gallon jug,” Behr said. “It ain’t gonna work.”
The Butte County Public Works Department identified multiple challenges in addressing flood risk in the Rock Creek and Keefer Slough drainage basin, which spans from Highway 99 east to the foothills, reaching up to 3,800 feet of elevation.
The area where water flow splits between the creek and slough sits on privately owned property and does not have controls to ensure an even split, according to Public Works Director Dennis Schmidt. Most of Keefer Slough also is privately owned and maintained sporadically. Further, neither Rock Creek nor Keefer Slough has sufficient room to contain a 100-year storm.
It’s also likely, according to Schmidt, that housing developments in the area have added additional stress to the drainage system. To that end, he said, staff can modify standards already in place to require new developments to capture more storm water, but more comprehensive—and more expensive—projects likely will need to be considered long-term.
“We can come back with a set of design criteria that will not make the problem any worse,” Schmidt told the board. “I don’t know if we can correct anything there. As a matter of fact, I can tell you we can’t correct it on the backs of the developers building detention, but we can get to the point where we’re not making it any worse.”
Supervisor Tami Ritter jumped in.
“That’s a low bar there, Dennis,” she said.
“We have a very impacted … drainage basin,” he replied. “It’s very difficult to make that better short of hard-dollar improvements into that channel.”
Meanwhile, development has continued in the drainage basin. About 80 potential new residential lots are in the application process with the county, according to staff, and an additional 100 lots are in the preliminary phases. A motion for a 45-day moratorium on building permits was supported by Supervisors Debra Lucero and Ritter but ultimately failed. It was noted that parcel and subdivision maps already in the application process would not be required to comply with any possible future stormwater retention standards.
Nevertheless, Lucero, seizing on concerns raised by residents of rising nitrate levels in their drinking water, said a moratorium could be seen as a good-faith gesture showing the county has heard their concerns and will examine the issues further.
Ultimately, the board directed county staff to pursue a slew of flood risk reduction measures, including increasing required stormwater detention volumes, updating building requirements, supporting more channel maintenance, exploring designs to stabilize the bifurcation, and developing a project following a flood risk reduction study. The timeline for completing those items was staggered over two years, with project development possibly arriving in 2022.
Meanwhile, Butte County Public Health was tasked with giving a presentation in early March on the nature of nitrates and finding outside agencies that could help identify any possible source for increased levels in the drainage basin.