Efforts by several cities to curb invasive species like knotweed continue to yield benefits and data in the Valley. Last week, local knotweed fighters from Warren, Waitsfield and Fayston, along with the UVM interns working here this summer, met with two UVM staff members to look at some high-resolution images of local floodplains, riverbanks and knotweed infestations.

Hans Estrin, coordinator of the UVM Extension Ecology Planning Laboratory, and Adam Zylka, UVM engineer in the Spatial Analysis Laboratory (SAL), were in the Valley on Aug. 8 to deploy two different types of large drones that captured extremely high-resolution images of the Mad River and its watershed from 400 feet up. The images are so high resolution that they provide specific species data and can be used to assess vegetation changes over time in specific areas, Estrin explained.

“For communities like Warren, Waitsfield and Fayston that are working together to manage invasive species, this work helps visualize their progress over time, like a scoreboard,” Estrin said.

“This work is completely new because SAL is doing it across the state, and it’s a godsend for the Valley because of the quality of the images. They’re high-resolution images stitched together with geothermal overlaps, showing the full spectrum for infrared and ultraviolet on maps,” Estrin said.

Two different drone flights took place. The first was an infrared/ultraviolet drone and the second was a LIDAR drone that sent laser waves into the vegetation and sediment, showing what was growing and what had been deposited at a site, including flood plains.

“This will allow people to see the impact of their work and the consequences of the floods,” Estrin stressed.

“Over time, it can show historically how floodplains and rivers move,” he added.

Jito Coleman, chair of the Warren Conservation Commission and one of the leaders and founders of the tri-city conservation commission initiative to combat the knotweed problem, said the UVM SAL drone mapping is an excellent tool to evaluate multi-city efforts both in terms of what is happening along the river corridor and in the floodplains.

“The aerial survey helps us see whether our efforts to reduce knotweed at higher elevations so it doesn’t get washed downstream during floods are working. And along the river corridor itself it helps because in some places the knotweed is so dense that we can’t walk along the river bank,” Coleman said.

This type of imagery – and access to these tools through UVM – helps local conservation commissions and volunteers identify and map the boundaries of knotweed infestations, Coleman explained.

“We believe that over time it will not only tell us how the river is moving at the smallest level, inch by inch and year by year, but it will also tell us whether it has moved where the knotweed is or not and where the knotweed is going. We know that knotweed has shallow roots. We believe – and the science strongly supports this belief – that knotweed accelerates erosion. So knowing where it is and how it affects the river is critical,” Coleman said.

Coleman said cataloging the data is becoming even more important due to increasing rainfall in Vermont and the increasing number of floods.

“In this part of Vermont, a 100-year flood is a flood defined as 5.5 inches of rain in 24 hours. We now know that those numbers no longer reflect what we are seeing,” he said, referring to 100-year floods in July 2023, December 2023 and July 2024.

“This means that the numbers used to design our infrastructure are no longer valid by a factor of two, three or more,” he stressed.