LocationAlhambra , CA United States
As you drive south down Palm Avenue in Alhambra, you see it rising up in the distance — a large glass cube that houses the headquarters for the Los Angeles County Department of Public Works.
On sunny days, white clouds move across the 15-story building, their movement is reflected in the pristine blue window panes. On stormy days, the building retains its blue color, while inside, down one of the building’s narrow hallways, behind a set of double doors, several L.A. County Public Works employees are sitting at their desks, busy answering the phone and looking at large computer monitors, making sure Los Angeles County residents who call in are safe from flooding. Next door, representatives from each Public Works division sit at long desks, each equipped with a landline, to coordinate a response to weather or public emergencies that affect county infrastructure.
L.A. County Public Works is one of the busiest departments when it rains, managing a network of 14 dams, which stores stormwater and allows it to come down the Los Angeles River, the San Gabriel River and other local rivers at a manageable pace. The county also has 300 debris basins or “neighborhood dams” that stop debris from flowing into neighborhoods and also slow the flow of water runoff to prevent floods.
This infrastructure also includes spreading grounds that capture water for treatment and storage, so that residents can use it as drinking water. “[The spreading grounds allow] the storm water to percolate into the groundwater reserves,” said Steven Frasher, a public information officer for L.A. County Public Works.
As the public works center for the largest county in the country, L.A. County Public Works’ 4,000-strong engineering and support staff is tasked with building and maintaining public infrastructure, including roads, bridges and airports. The department also coordinates emergency management in the event of natural disasters like wildfires and earthquakes with the aforementioned 24-hour dispatch and an on-call emergency operations center.
A network of rain gages are located throughout the county and provides information on rainfall totals and intensities as storms move through the region. At the Alhambra headquarters, the department’s Storm Boss office receives this information and makes sure the county’s infrastructure is diverting and capturing that water properly. In the field, workers are patrolling the vast infrastructure to make sure it’s working.
“This information is very helpful to the Storm Boss in making operational decisions at the dams and spreading grounds to provide flood protection and capture stormwater for groundwater recharge,” said Senior Civil Engineer Eric Batman.
During a major storm, a team of four civil engineers rotate in the Storm Boss position during 12-hour shifts, where they make decisions about when to store and release water.
L.A. County stretches from the South Bay to the Antelope Valley and east into the Pomona Valley. It inhabits an area 4,751 square miles and has a population of over 10 million people. Monitoring infrastructure and the environmental effects on it is an enormous task.
“During storm events, rainfall amounts can vary significantly throughout the County, with foothill and mountain areas often receiving twice as much rain as downtown Los Angeles,” Batman sad. “When we see the radar showing heavy rain cells moving into Los Angeles County, and the rain gages really start to pop as rainfall amounts increase quickly, it can really get our adrenaline going.”
Since the start of the storm season, October 2018, downtown Los Angeles has received 16.3 inches of rain. In addition, L.A. County Public Works infrastructure has captured 71,000 acre-feet (23 billion gallons) of storm water.
Flood Prevention after the Woolsey Fire
The Woolsey Fire burned through almost 100,000 acres in the Santa Monica Mountains last November. Yet the risk did not end with the fire being contained. In advance of the rainstorm from Jan. 14 to Jan. 17, L.A. County Public Works employees were in the areas burned by the fire to assess the risk of mudslides due to increased soil erosion.
“Mud and debris flows are unique in terms of disasters or emergencies in that there is some small amount of forecasting that we can do that something is going to happen,” said L.A. County Public Works Strategic Communications Manager Kerjon Lee. “So we know in areas like Malibu or Calabasas and Agoura, because there was the Station Fire, we can look at the slopes and say, ‘Ok, it’s highly likely that this area is going to be impacted, because it’s at the bottom of a canyon.’ ”
L.A. County Public Works also clears roads of debris so that people can use them safely. In areas with high mudslide risk, they work with the fire department and the Sheriff to evacuate residents.
“Usually it’s one, sometimes it’s two individuals in the truck and they’ll be patrolling the whole system to make sure there are no issues, there’s no tree branches and everything is flowing as it should be,” Lee said. “And also the spreading grounds have operators too to monitor and make sure the water is going where it should be.”
In reality, flood control is a yearlong endeavor, with L.A. County Public Works having to clear debris that builds up in debris basins and behind dams after a rainstorm. “As soon as a storm is over, or as soon as a wildfire is over, crews are into those areas immediately to clear out the debris behind the structures, so again that they’re ready for the next storm event,” Frasher said.
Climate change has made both flood control and water conservation efforts more urgent than ever. In November, L.A. County voters adopted a parcel tax to fund more stormwater capture projects, after a five-year drought caused severe water shortages in the county.
What Alhambrans can do
L.A. County Public Works also works year-round to educate residents on how they can be safe from floods. Alhambra is at a lower risk of flooding because it’s relatively far away from the foothills and the L.A. and San Gabriel Rivers, where the risk is higher.
But there are still things that can be learned to reduce the risk of flooding.
“It allows the teachable moment to have people not leave their garbage cans out on the street when a storm is predicted to be coming in, not have your car parked in front of a catch basin, which is the big drain at the end of a block,” Frasher said. “Quite often having one of those structures blocked is the biggest impediment that a neighborhood faces and really needs to be addressed on a neighborhood level.”
Residents throughout L.A. County can prepare themselves for the rain by checking out L.A. County Public Works’ web portal, with emergency preparedness information, road closures and even resources on flood insurance. “It’s always there year round for people to prepare themselves for the upcoming storm season,” Lee said.
For more information on how to deal with rain and flooding in L.A. County, visit L.A. County Public Works’ LA Rain portal.