A University of New Brunswick professor says recent sinkholes that have developed on properties northwest of Fredericton is a result of shifting sediment.

Two different homeowners in the Upper St. John River Valley have discovered sinkholes on their property.

Adrian Park, an expert in structural geology at the University of New Brunswick, said both locations are made up of sediments deposited by the river.

And, he said, if there is a layer of looser gravel in between the sands and mud then groundwater can start to dig away.

"Rather than just seeping through the sediment, [water] can actually start carving channels and cavities, particularly if you have something like a buried tree root that has rotted out or even an animal burrow," Park said.

"And the water can then swirl and produce a cavity underground. That cavity becomes unstable and falls in. And you have a sinkhole."

Sinkholes are not common in this area, but something that was likely helped along by a week of steady, heavy rain.

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A sinkhole developed on Danny Roy's home in Temperance Vale. CBC

In Temperance Vale, Danny Roy was trying to mow his lawn when he stumbled upon a sinkhole.

He said the mower wasn’t working properly and then he felt it dip.

"I thought that was a little odd, so I got off my mower and walked over to the spot, and stood there for three or four seconds and down I went. One leg went clear down, then, [it] startled me, [I was] quite a scared," he said.

"I got out pretty quick and got a shovel and stuck the shovel down through, poked the hole a bit wider, stuck the shovel down through, to see how far the hole was and all I could see was water and pouring, running quite fast, and I couldn't touch bottom with my shovel."

Roy said it has taken 22 loads of dirt and rock to fill the hole

A similar sinkhole was discovered on Roy Carson’s home, which is about 25 minutes up river. A man was over doing some yard work and told him he had a hole.

"He said, ‘It's more than a gopher hole!' And I came out to look at it and I couldn't believe it," Carson said.

Carson was able to plunge a two-metre rod into the sinkhole.