NASHVILLE, Tenn.—Music City USA is cleaning up from torrential rains that caused the Cumberland River to flood parts of downtown Nashville, Tenn., and nearby suburbs, damaging thousands of homes and businesses.

Flash flooding from storms that swept through Kentucky, Mississippi and Tennessee earlier this month caused significant damage in Nashville, where Mayor Karl Dean last week estimated damages in the city alone could top $1 billion, according to reports.

There have been 30 reported deaths in Tennessee, Mississippi and Kentucky due to the storm.

Gary Kerney, assistant vp of the Insurance Services Office Inc.'s Property Claim Services unit, said a catastrophe serial number, which is assigned when the estimated insured losses exceed $25 million, had been assigned for insured property damage caused by the severe weather and flooding, but said that “PCS has no information on the extent of insured damage nor information regarding uninsured losses.”

Flooding extensively damaged the Gaylord Opryland Resort & Convention Center, which officials said resulted in more than $75 million in damage to the hotel and will close it for up to six months, according to reports. The Grand Ole Opry House as well as the Country Music Hall of Fame and Museum also were hit by the flooding.

“The Opryland area suffered massive devastation,” said James H. Costner, Nashville-based senior vp of Willis Group Holdings P.L.C.'s national property practice. He said the city's banking and legal district was without power a majority of last week and that tens of thousands of trucks were submerged, as Nashville is a major transit hub for distributors.

In addition, one of two of Nashville's water treatment plants was disabled.

“The insured losses from this are going to be major,” Mr. Costner said.

The National Flood Insurance Program, which is run by the Federal Emergency Management Agency, may cover some losses experienced by businesses and homeowners that purchased the coverage. However, Mr. Costner and other insurance experts said flooding reached areas that are not federally designated flood zones.

According to FEMA, Nashville and Davidson County, Tenn., had 4,100 NFIP policies in force as of March.