Leo Zwetsloot, a Dutch tourist staying at the Bukit Lawang Cottage hotel in Bukit Lawang village, told BBC News Online that hardly any of the buildings in the area were left standing.
"There are only 10% of the houses left, we just see huge piles of trees swept down by the water.
"Imagine a pile of matchsticks. There are piles of trees like that, but they are 30 metres high."
Mr Zwetsloot said there seemed to be about 20,000 trees scattered around the village.
He said they were swept down the river after two days of rain, knocking down bridges and destroying houses.
Over one half-hour period the water level had risen by five metres, he said.
Although Mr Zwetsloot had no idea about the casualty figures, he said there were undoubtedly dead and injured.
"There has to be a big military operation. Houses are crushed under trees and people are stuck in their houses. A lot of the houses are swept away. Totally gone."
Mr Zwetloot said that the damage had occurred after a landslide was caused by the heavy rains.
He said the area had been heavily logged over the last few years.
But his immediate concern was the need for an emergency relief operation.
"We are stuck here," he said.