OWNERS had to stand on riverbanks and watch their animals drown at the height of Sunday's flooding on the Gold Coast, an RSPCA inspector says.

The animal welfare body estimates around 100 cattle and a large number of horses drowned in the Coomera River after the northern end of the Gold Coast received more than 360mm of rain in 24 hours over the weekend - the most intense day-long deluge in a century.

Summer Heath-Crilley, an RSPCA inspector on the Gold Coast, said the scene was heartbreaking.

"There were people on the side of the bank seeing their animals being washed down and there was no way anyone could put a (rescue) boat in the water," she told AAP.

"People were screaming out thinking they were seeing their horses and screaming out their names.

"It was very distressful to be a bystander and not be able to do anything."

Ms Heath-Crilley said she would be joined by five RSPCA inspectors from Brisbane to patrol Gold Coast rivers in two boats over the next few days.

She said there was little or no hope of finding live animals but they were concerned to recover dead animals for health reasons and to give pet owners closure.