A Perth couple caught in deadly US floods in Boulder, Colorado, said chaos had gripped the city as they bunkered down in an evacuation centre.
Zoe McGill, 27, and her partner Fred Baynes, 28, were evacuated from their apartment late on Wednesday and were sleeping on a yoga mat on Friday night in a building with 200 other people.
"Although not as intense as the Brisbane floods, it is still scary," Ms McGill said.
"All bottled water has sold out, more people are being evacuated and the floods are getting worse … A one-in-100-year flood and we are in the middle of it."
Rare downpours this week unleashed flash flooding across the State, stretching 210km from Fort Collins to Boulder, Denver and Colorado Springs.
Three people died, another person is missing and thousands fled to higher ground on Thursday as water toppled buildings and stranded cars.
Boulder, a city of 97,000, and towns along the Rockies Front Range were hard hit as waters streamed down mountains, through canyons and into homes.
Ms McGill, a marketing co-ordinator from Claremont, and Mr Baynes, a physicist from Subiaco, have lived in Boulder since July.
"We live on Boulder Creek in a Colorado University faculty apartment and on Wednesday we noticed the creek was exceptionally high," Ms McGill said.
"At 9pm the flood warning sirens came on and at 11pm the police evacuated us to Athens Court dormitory with 200 others.
"By Thursday the water was at our apartments' bottom floor."
President Barack Obama approved disaster assistance.
Boulder emergency management spokesman Andrew Barth said several buildings collapsed and Sheriff Joe Pelle said some towns were cut off.
A dozen major roads in north-eastern Colorado were closed with major damage from flooding, mudslides and rockfalls.
The latest deluge began on Monday with steady rain through Wednesday that grew heavier overnight.
Driving rain was almost unabated in Boulder on Thursday.