Geologists are raising concerns about the potential for dangerous landslides on Burlington's Riverside Avenue, a historically unstable hillside made worse by recent heavy rains.

If you're a regular walker on the River Walk trail, you've probably noticed a sign warning that the trail is closed. The reason is a landslide which came down from Riverside Avenue in the Halloween storm.

"The floodwaters have been here. You can see the vegetation knocked down in the direction the water was flowing," said Paul Bierman, a University of Vermont geology professor.

He takes the River Walk home from work and picks up on nature's cues that many might miss, like trees tilting sideways. "That's probably the best indication that the slopes are unstable," Bierman said.

In April he noticed something else. "I saw some big cracks in part of the ground in one of the parking lots there that I was walking through. A couple cars with their wheels hanging off the ground and I thought, something's odd here," Bierman said.

By early October the fissures were big enough that he warned the city and state that a landslide was coming. "I saw the tension cracks, I saw the steep slope, I saw the material that had been dumped there and I thought -- big rainstorm and this is going to come down," he said.

And three weeks later it did. As city streets flooded Halloween night, the ground gave way, sending tons of material down the bank.

It's not the largest slide to happen on Riverside Avenue. Photos of the area in 1955 show the road was wiped out. It was rebuilt with fill. That 1955 slide was right next to the area that gave way during the Halloween storm.

"That implies that this area is capable of generating really large landslides which -- if one of those were to happen underneath one of these buildings, if people were in it -- would result in fatalities," Bierman said.

He's particularly worried about the foundation of a yellow house that's teetering on the edge. "When you see ground cracks, that's an indication typically that there's a landslide that's going to happen," he said.

We went to speak with residents to see if they were concerned for their safety. The house is rental and no one was home, but business owners on either side say they're aware the slope is slipping.

Ed Couillard says he's been trying to protect Burlington Collision Center's property ever since Tropical Storm Irene eroded his driveway. He allowed a local tree service company to put wood chips and logs there to try to shore up the side. "I certainly don't want my building to go over the bank," he said.

Couillard says the city and state recently visited him and told him he needed engineers and a permit to do it correctly. He says it's frustrating. "I don't really know what they expect me to do," he said.

"I've been here for 30 years. I don't want to go nowhere. This is my livelihood," said Wallace Hall with Hall's Hitches and Welding, another nearby business. Hall has roped off part of his parking lot.

Reporter Cat Viglienzoni: And you're not concerned for your building?

Wallace Hall: No, I'm not concerned for the building. I don't think anything behind me has moved in forever years I've been here.

He's hoping for help from the city and state so he can stay. "I don't really want to think about walking away I mean -- it's 30 years here," Hall said.

We went to the Burlington Public Works Department -- to see if he's going to have to move. "It really depends on what the experts recommend. I would say it could be potentially very expensive," said Bill Ward, DPW's director of permitting and inspections. He says the city is concerned about the area and that assessments are planned soon to figure out how stable the ground is around these properties. In the meantime, the city wants landowners to leave it alone. "Any added weight could create a much bigger problem."

Buildings have been condemned along Riverside Avenue before because they were hanging over the bank. Ward says, the fate of these depends on what engineers say.

Reporter Cat Viglienzoni: Is there a concern for that home and the safety of the occupants inside?

Bill Ward: What the city would want is some geotechnical engineering to determine exactly what the additional risks are.

Reporter Cat Viglienzoni: Is there any concern for Riverside Avenue -- the road itself?

Bill Ward: I don't think so, not at this point.

Bierman says he isn't so sure. "This is what we teach students causes landslides," he said. He says he wants to see a bigger discussion about the safety of building on steep slopes -- and he's got a different route home now. "You're taking your chances if you walk across that."

We reached out to the state geologist and a landslide expert at Norwich University to get their take on the situation. Both have visited the area and said the ground cracks at the top of the slide indicate that the slope could potentially fail, but they also said geotechnical experts would need to determine if the structures are at risk.