Federal officials have expanded their estimate of the number of homes and businesses along the Los Angeles River that could be inundated by a flood north of downtown.

More than 3,000 parcels near the L.A. River could be submerged by an average of 5 to 10 feet of water when a 100-year flood hits, according to a new study released Monday by the Army Corps of Engineers.

Residents of Atwater Village and Elysian Valley would be the most affected by such a flood, while parts of Griffith Park, Glendale and Burbank would also see flooding, the study says. The largest predicted flood depth would be 18 feet in Griffith Park.

Property owners with federally backed mortgages will be required to purchase flood insurance, said Army Corps spokesman Jay Field.

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