The True Scale of Flood Hazard Facing Los Angeles

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.