New warnings about risk of major flooding on L.A. River amid new development, revitalization

For decades, urban planners and city leaders have envisioned transforming the gritty, concrete-walled Los Angeles River into the backbone of a new kind of city, one with the riverbed restored to nature, surrounded by parks, trails and new residential developments.

But Los Angeles this week received a stark reminder that the river that cuts through the region — much of the year just a trickle — can become a dangerous torrent during periods of intense rain.

A new U.S. Army Corps of Engineers report found that more than 3,000 parcels north of downtown Los Angeles in neighborhoods such as Atwater Village and Elysian Valley could be submerged by an average of 5 to 10 feet of water in the event of a 100-year storm. It also found that other areas such as Griffith Park, Glendale and Burbank could see significant flooding.

Property owners with federally backed mortgages will be required to purchase flood insurance because of the findings, federal officials said.

Additionally, developers could face new restrictions such as having to build the first floor at a higher elevation for properties within the flood zone, according to city engineers.

The Army Corps released its study as the city pushes ahead with a plan for ripping out the concrete channels of the river and restore natural plant life. The concrete walls were installed to better protect the city from periodic flooding when the L.A. river overflowed its banks.