The death toll from catastrophic flooding in Texas rose to more than 100, as rescuers continued their grim search for people swept away by torrents of water.

Among the dead were at least 27 girls and counsellors who were staying at a youth summer camp on a river when disaster struck over the Fourth of July holiday weekend.

Forecasters have warned on Monday of more flooding as rain falls on saturated ground, complicating recovery efforts involving helicopters, boats, dogs and some 1,750 personnel.

"There is still a threat of heavy rain with the potential to cause flooding," Texas Governor Greg Abbott said in a statement Monday, with the number of victims expected to rise.

President Donald Trump confirmed he planned to visit Texas on Friday, as the White House slammed critics claiming his cuts to weather agencies had weakened warning systems.

After floodwaters receded, a dramatically altered landscape was revealed, with uprooted trees, eroded trailers and debris-strewn riverbanks.

Here are some images of the damage and rescue efforts: