How LA is reimagining flood infrastructure amid increasing flood risk

As many as 429,000 Southern California properties have an 80% or higher chance of flooding by 2053.

ByAnabel Munoz and Grace Manthey KABC logo
Monday, October 9, 2023
How LA is reimagining flood infrastructure
As many as 429,000 homes and businesses have an 80% or higher chance of flooding by 2053 in SoCal counties, but communities, non-profits and government agencies are developing programs to educate and restructure water issues in Southern California.

SUN VALLEY, CALIF. (KABC) -- Southern California has gotten a lot of rain.

But in Alicia Gonzalez's Sun Valley neighborhood, she said they've been relatively safe when it comes to flooding.

"It'll only last for about maybe 20 to 30 minutes, and then the water will go down. So, it's perfect. It's not a problem like it used to be," Gonzalez said.

She's said her parents purchased the house where she lives back in the 1980s, and she's been in and out all her life.

The flooding used to be so bad, one time a neighbor rode down the street in a canoe. Her father would use his van to help students in the neighborhood cross the street so they could get to school.

About ten years ago, she helped rally her community together to secure funding for a retrofitting project. The project was run by multiple partners like Los Angeles City, Los Angeles County and non-profits.

Flooding and water resources for Southern California

She said she remembers organizers going door-to-door to try to get the neighborhood involved, and she became friends with one of them.

"And then from there, we just kept talking. And I'm a big mouth, I'm very friendly," she said. "So, I just kind of started getting involved."

The project included infrastructure like:

  • Catch basins to divert water from the street
  • Swales on the edge of the properties, which are shallow channels where water can run off or soak into the drainage systems
  • Rain barrels to collect rainwater from roofs
  • Permeable pavement that allows water to soak into the ground instead of running off
  • Trees
  • Drought-tolerant plants
  • A reimagined alleyway in the neighborhood with a pedestrian path, rocks at the ends to capture trash in the event rain does come, and an infiltration system underneath to capture water.

Carlos Moran from the Council for Watershed Health, an LA County-based non-profit that helped with this project, said the area is designed to hold millions of gallons of water a year.

"That being infiltrated, is being treated and is becoming water supply for future generations," said Moran.

"Projects like that are examples of green infrastructure projects where agencies, government agencies, philanthropy, and nonprofits, and residents can come together to take active control of their neighborhoods," he said.

Flood risk in Southern California is increasing, and most don't have flood insurance

Climate non-profit First Street Foundation estimates that in Southern California many as 429,000 homes and businesses have an 80% or better chance of flooding at least once by 2053.

Up to 90% of those properties may not have flood insurance, according to data from the Federal Emergency Management Agency.

Mike Peterson, the Deputy Commissioner on Climate and Sustainability at the California Department of Insurance said the flood insurance "protection gap" is "a risk awareness issue."

Many might not know that they live in a flood risk area, or that flood insurance is an add-on to regular property insurance, not a part of it.

FEMA manages nearly all flood policies in the U.S., requiring them in neighborhoods they have classified as flood risk areas.

But experts said those FEMA flood risk maps may not accurately depict flood risk.

"FEMA maps flooding, mostly from rivers and streams and coastal flooding, they don't map flooding from rainfall," said Jochen Schubert, a research specialist at UC Irvine with a focus on flood hazards.

He and his colleagues have developed their own ways of modeling flood risk in the LA area and he said there's been change in the land development since the FEMA maps were built. More concrete, for example:

"The rainfall directly falls onto these surfaces and very quickly moves from streets and pavements around homes into the river channel," Schubert explained.

"And so that rainfall accumulates really quickly in these channels and water levels build up very fast and usually much higher at a much higher level than if there was a lot of green space," he said.

Because many of the FEMA maps were created years or even decades ago, "they don't capture these changes," Schubert said.

Schubert, who is familiar with the First Street Foundation maps, said the model includes flooding from rainfall, unlike the FEMA maps.

"Hats off to them, they developed a method to model flood hazards across the whole nation. That's a very complicated task," Schubert said.

First Street Foundation researchers say their flood models capture 2.2 times as many properties with significant (a 1-in-100 year or greater) annual flood risk as those in FEMA's comparable flood hazard areas.

By First Street Foundation's count, about 9.8 million of its 17.7 million significant flood risk properties are outside of FEMA flood zones nationwide.

As a result, First Street Foundation researchers believe many of those property owners have received no information from FEMA and may not fully understand - or underestimate - their future flood risk.

The UCI Flood Lab models are different from the First Street models, mostly because of the fine detail of maps they use to model, said Schubert.

First Street's models "apply to different kinds of environments," whereas, "we tend to focus on places like L.A., for example, or Miami-Dade County where we know we can find very fine resolution topographic data."

Whether you compare to the UCI or First Street Foundation flood risk predictions, Schubert said FEMA is "likely under-estimating the number of properties" at risk for flooding.

Peterson, from the Department of Insurance, said not only are the FEMA maps potentially outdated, "but these are risks that are accelerating to a certain degree because of climate events."

Mark Pestrella, Director of Los Angeles County Department of Public Works said the combination of more development, more concrete and more rain increases runoff and flood risk.

"And although we've been able to deal with that over the years. what we're seeing with climate is the potential, at least locally, for some of those interior drainage systems to not be able to handle the amount of flooding and more rain that's coming," Pestrella said.

"And that definitely is a challenge when we're trying to address water quality, water supply and flood risk," Pestrella continued.

All three of those issues can be addressed by creating more parks and green spaces, experts said.

"The current state is we take rainwater, and we create super highways, you know, drainage systems that take that water away from us as soon as possible to protect human life," explained Moran from the Council for Watershed Health.

"But nowadays, we need to think about how can we collect that water? How can we harvest it? How can we maintain it and hold it close to us, so that we can increase our water supply so that we can manage a work with that water to provide irrigation," he continued.

Rethinking our water infrastructure is not an easy task but community input and education is important

This isn't an issue that can be fixed in "a year's time," according to Moran.

"This is something that takes many years to be able to address," he said.

And experts say it will likely take longer, unless local officials, non-profits and community leaders educate and listen to residents about the risks and the solutions.

"If there's any time to really get involved, and to really get to know and educate oneself about your environment and flood risk and flood issues and the connection between rain and people, it's now," Moran said.

"It should have been done before, right? When the city was built. But they didn't have the information," he continued.

Mark Pestrella, from LA County Public Works, said spreading information to as many people as possible is one of the goals of the department going forward.

"Educating the cities, educating their flood plain managers, and then all the way down to the residential property owner. What is my flood risk? What does it look like?...What is our plan when it rains in LA?"

And even for researchers studying flood risk, community input and education is important.

"We reach out to decision makers and stakeholders, and we run focus groups where we ask questions," said Jochen Schubert from UCI.

"We sort of gain confidence that our model reflects what people see in neighborhoods, but also that we are addressing the needs of decision makers and case they want to use our data for decision making purposes and adaptation plans and so on," he continued.

There are multiple efforts underway to help mitigate flood risk and educate the public

In 2018, the county passed Measure W, a parcel tax that funds the Safe Clean Water Program which invests $280 million annually into stormwater capture projects and programs.

So far, the program has funded more than 300 projects and studies. More than 200 of those projects improve flood protection, according to the program's dashboard.

"We are cutting up the pavement all over LA. County," said Pestrella. "I know it sounds simplified, but that's truly what we're doing. We're actually either diverting to a place where the water can get in the ground or we're opening up, at the neighborhood level, places where water can go into the ground at their street level and instead of running off to the ocean being wasted."

But there's more.

At the end of 2022, the Los Angeles County Board of Supervisors approved a motion directing the County's Public Works department and Chief Sustainability Officer to assess flood infrastructure.

Pestrella said as a part of that there will be a series of seminars at city and local community levels communicating the department's findings.

"I really do encourage property owners in Los Angeles County to take advantage of their tax dollars by getting in touch with us. And also following up with us on these seminars that are coming, and these education moments down to the community level about their flood risk and what they can do to create a more resilient LA county and a more resilient neighborhood," Pestrella said.

What can you do in your home or neighborhood to help with flood risk?

If you're looking for ways to harden your home and family against flood risk, Pestrella said LA County Public Works will do a virtual or in-person assessment of your home's risk.

Carlos Moran said one of the easiest things you can do in your neighborhood to mitigate flooding is plant a tree.

"When it rains, that tree holds that water, it slows it down, it spreads it where it needs to be spread," Moran said.

Back in Sun Valley, Gonzalez said she loves all the trees and plants they have because of past community efforts.

"We feel like we're in the mountains," she said.

And, she encourages other communities educate themselves and dive into projects like the one that transformed her street.

"If they have the opportunity to get the help I it. It's an amazing project, do it," Gonzalez said.