Bella Bennett and Paul Bierman: A solution to landslide risk in Burlington

This commentary is by Bella Bennett, a doctoral candidate at the University of Vermont who studies human-landscape interactions, and Paul Bierman, a professor of environmental science and natural resources at UVM who has studied landslides and erosion for nearly 40 years.

Heavy rainfall is having a devastating impact on our state, and we need strategies to mitigate future hazards to people, infrastructure and the environment. Increasingly, these intense rainstorms cause floods, and sometimes trigger landslides .

We’ve been studying the history of landslides, their impacts on people and property and landslide repairs along Riverside Avenue in Burlington, Vermont, for years. We’re writing to share some of our recently published findings and suggest ways we can use them to better prepare this slope — and others across the state — for increasingly severe weather and heavy rainfall, a critical landslide ingredient.

People and their actions over the past century have unknowingly but severely exacerbated the landslide risk along Riverside Avenue. How? By dumping waste (aka “fill”) onto slopes — garbage, construction debris, soil, junk cars — all without a plan. That material is, like sand, not cohesive. It doesn’t stick to itself well or to the slope below.

Imagine making a sandcastle and then haphazardly dropping handfuls of loose sand on top — you can guess the outcome. Even if those handfuls of sand don’t immediately cascade down the side or collapse the castle, the combination of precariously placed new material and a splash of water is likely to do the trick. In a similarly haphazard fashion, people have been dumping material along this and other slopes across the state for decades.

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With every dump truck load of fill, the risk piles up. On Riverside Avenue, we’ve documented at least 20 landslides along less than a mile of roadway in just the last 70 years — almost all involved material people dumped onto the slope, and many followed heavy rainfall events.

In the past 30 years, at least two buildings on Riverside Ave have been undermined by landslides , then condemned and demolished, leaving the property owners in a financial lurch. The slope continues to pose a risk of slides today. Following the 2019 Halloween landslide , a 2020 slope stability report identified six at-risk properties . So, what can we do?

With the knowledge we now have, we can and must act now to prevent those who live and work along the slope from facing future harm. To ensure their safety, we need to make sure the slope is stable and able to resist heavy rainfalls which increasingly impact Vermont, causing landslides that destroy roads and homes . Our concern is for the safety of people who live, work and travel on Riverside Avenue. Delay is not a responsible option.

Based on what we have learned about Riverside Avenue, our collective expertise in landslide science and our shared commitment to environmental justice, we strongly suggest that the northern side of Riverside Avenue be fully reforested. Why? Because decades of science show that tree roots stabilize slopes and prevent landslides , even in Vermont .

We can protect our community by buying out and removing the buildings (and impermeable surfaces like paved parking lots) along this slope, and replacing them with deep-rooted native plants . By increasing vegetation and preventing access (and thus dumping which continues to this day along the slope) we can both stop the accumulation of new unstable material and increase the stability of the material that was previously added to the slope.

Ours is a comparatively low cost, natural and effective solution to a problem that over decades has cost the city, state and property owners untold sums over the past 70 years. For context, we found records of repair costs for five of the historic landslides, and these totaled over 1.4 million dollars (corrected for inflation), which doesn’t even consider costs to property owners.

It is important to start the reforestation process now. As the old saying goes, the best time to plant a tree is 20 years ago, and the second-best time is today. For this strategy to work, newly planted trees will need time to grow deep, fortifying roots . The sooner we plant them, the more ready the slope will be to meet a future characterized by more frequent and heavier storms . A proactive rather than reactive approach by planners, regulators and city officials can prevent future hardships .

Instead of a risky, landslide prone slope, Burlington could soon have a beautiful linear park — a public green space, where trees naturally increase slope stability and prevent further dumping. If we deploy this strategy successfully along Riverside Ave, we’ll have a great model to apply to similarly landslide-prone slopes across the state.

For safety’s sake, it’s time to invest in preventing further slope failures along Riverside Avenue. It makes sense to use a natural, cost-effective and minimally environmentally invasive approach.

Read the story on VTDigger here: Bella Bennett and Paul Bierman: A solution to landslide risk in Burlington .