Nariel Valley and Thowgla Valley were both hit by an intense storm on Monday which caused "black rivers" of mud and debris to wash through roads and sheds, leaving a putrid odour and significant clean-up effort required.

Nariel Valley's Belinda Attree said about 27mm fell in less than half an hour on Monday, causing devastation just as the region starts to recover from the Upper Murray bushfires.

"We just can't win a trick at the moment," she said.

"I know a farmer about five kilometres up the road from my place who had brand new fences put in last week after the fires burnt his fences.

"Now they've been destroyed again. It's devastating really."

Mrs Attree said the sudden storm temporarily turned roads into rivers, felled trees and even washed ash sediment into paddocks that had survied the bushfires, compromising the soil.

She said the rain had hit the already struggling community hard

"It disheartening," she said. "There's been so much destruction and the wash off is going into the creek...it takes all the oxygen out of the water and kills the fish."

Across in Thowlga Valley, Charlie O'Connor said a black river of debris and mud cascaded at a frightening speed down the hill where her house sits.

She said 17mm had fallen as light rain across the weekend, but Monday's storm caused 22mm to fall within 15 minutes.

Mrs O'Connor said her rain water tank had gone from 17mm full to overflowing in five minutes.

"There's not much vegetation or ground cover left," she said.

"So within five minutes an absolute river was coming down the hill... a black river that came right up to our doorstep."

Mrs O'Connor said the rain had eroded land between the shed and carport, with a foot of mud left behind.

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"It's not normal mud, it's putrid and black, it's absolutely gross, and it's inches and inches," she said.

"We still haven't cleaned up from the fire and now we have to clean up this."

Mrs O'Connor said she was lucky the black water had entered only her shed, not her house.

Mrs O'Connor said while she personally was focusing on being grateful her house and family had survived both fires and flash floods, she knew many in the valley were feeling hopeless.

"People have gone through trauma and for them it does feel like 'what now? How can we possibly come back?'," she said. "There's also a fear of how much more rain will come."

State Emergency Service operations officer Charlie Sexton said crews had received only a handful of calls as a result of the storms on Monday and Tuesday.

He said the major impact had been the closure of the Corryong-Benambra Road.

Mr Sexton said bushfires had reduced vegetation, increasing the chance of debris flowing across roads.