Overwhelmed rivers in much of southern Louisiana are receding slowly from record levels while crews in boats search for more people stranded in inundated homes after three days of torrential rains that killed seven people.
While the threat of flash flooding moved west into Texas, more than 11,000 Louisianans have signed up for disaster assistance. Many are waiting for the flood waters to drain away so they can determine what can be salvaged from their sodden homes and businesses.
Emergency crews already have rescued more than 20,000 people and continued to search for more after a storm dumped more than 61cm of rain in three days.
Aerial photographs on Sunday showed houses inundated in mud-coloured water with only their roofs visible while the bridge over the Amite River around Port Vincent, Louisiana, was almost underwater. People had become trapped overnight in their cars when the water rose on Saturday over parts of a major interstate around Baton Rouge.
While some rivers were receding on Monday, others downstream were still cresting.
The Louisiana flooding, which prompted US President Barack Obama to issue a disaster declaration, resulted in seven deaths, National Weather Service meteorologist Jennifer McNatt said. Four occurred when people drove vehicles into high waters.
The flood waters were expected to linger.
"It is going to take a while for that water to make its way out," McNatt, who is based in Fort Worth, Texas, said in a telephone interview.
Rivers in Louisiana crested at record levels in multiple places, with the Amite River reaching 14 metres in Denham Springs, 1.5 metres higher than a 1983 record, McNatt said.
Flooding in Texas was a concern on Monday with the NWS saying a flood watch extended from Houston to the Hill Country region in the central part of the state. Rain also could menace parts of Arkansas in the next two days, McNatt said.