The True Scale of Flood Hazard Facing Los Angeles

New research sheds light on how L.A.’s aging and poorly maintained infrastructure is putting hundreds of thousands more residents in flood hazard zones than previously estimated.

2 minute read

November 2, 2022, 11:00 AM PDT

By Diana Ionescu @aworkoffiction


Sandwich sign with "Flooded" and "CIty of Los Angeles Dept of Rec and Parks" sits in ground near orange traffic cone

L.A.'s stormwater system can quickly become overwhelmed during major downpours. | Logan Bush / Flooded

A new study warns that hundreds of thousands of Los Angeles residents are at risk for flooding, in part because of the city’s aging infrastructure, reports Raymond Zhang for the New York Times. The estimate far surpasses federal estimates, Zhong notes, “because the new study takes a more realistic view of the city’s water infrastructure, said the report’s lead author, Brett F. Sanders, a professor of civil and environmental engineering at the University of California, Irvine.”

The research team used lidar data to examine the city’s flood control channels, many of which are clogged with debris, and assess their true stormwater channeling potential. “Let’s not assume perfect performance from our infrastructure; let’s look at the most likely performance,” explained Dr. Sanders. “The researchers studied how water might move through the city by building a high-resolution topographic map, one that could show details as small as three meters across, or about 10 feet.”

Flooding is becoming a bigger threat to Angelenos as warmer air causes more intense winter rainstorms. “Today, California has a roughly 1-in-50 chance each year of experiencing another weekslong megastorm of comparable intensity, scientists estimated recently. Global warming has roughly doubled those odds compared with a century ago, they found.”

According to the article, the city’s low-income communities, many located near the Los Angeles and San Gabriel rivers, face some of the highest risk and costs for rebuilding and replacing damaged property. The mayor’s office says the city is working with the Army Corps of Engineers to update flood risk maps and develop new strategies for improving the city’s resilience to flooding. 

Monday, October 31, 2022 in The New York Times

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Use Code 25for25 at checkout for 25% off an annual plan!

Redlining map of Oakland and Berkeley.

Rethinking Redlining

For decades we have blamed 100-year-old maps for the patterns of spatial racial inequity that persist in American cities today. An esteemed researcher says: we’ve got it all wrong.

May 15, 2025 - Alan Mallach

Interior of Place Versailles mall in Montreal, Canada.

Montreal Mall to Become 6,000 Housing Units

Place Versailles will be transformed into a mixed-use complex over the next 25 years.

May 22, 2025 - CBC

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

May 21, 2025 - Diana Ionescu

View from hilltop residential neighborhood of downtown Los Angeles, California on a cloudy day.

LA Falling Behind on Housing Goals

Last year, the city permitted just 30 percent of the number of housing units needed to meet a growing need.

5 hours ago - LAist

Canada geese and ducks on the shore of a lake with red brick boathouse in background across the lake in Lincoln Park, Los Angeles.

Connecting Communities to Nature Close to Home

Los Angeles County’s Nature in Your Neighborhood program brings free, family-friendly wellness and nature activities to local parks, making it easier for residents to enjoy and connect with the outdoors.

7 hours ago - Los Angeles County Department of Parks and Recreation

Children inside large slide at water park.

Palmdale’s Beloved Water Park Gets $2 Million Upgrade

To mark its 20th anniversary, DryTown Water Park has undergone major renovations, ensuring that families across the Antelope Valley continue to enjoy safe, affordable, and much-needed water-based recreation in the high desert.

May 27 - Antelope Valley Press

Urban Design for Planners 1: Software Tools

This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.

Planning for Universal Design

Learn the tools for implementing Universal Design in planning regulations.