Saving Banks: Teaching How Roots Reveal Erosion Rates
Just as trees’ inner rings tell the story of their growth, their roots can reveal how quickly the earth is washing away around them. It’s critical information for addressing watershed problems.
Freese and Nichols’ Bryan Dick, left, and Ian Jewell, right, not only adapted a method for reading exposed tree roots to measure rates of riverbank erosion, but our team is using the technique for a growing list of clients.
Since last fall, our team has presented its deepening expertise on root dendrogeomophology at learning sessions and conferences across the South. And cities in multiple states are interested in applying the practice to assess the needs along their waterways.
Adding to the momentum, we recently co-hosted an all-day, hands-on training session with the Oklahoma Water Survey, a research and education project at the University of Oklahoma. Bryan presented along with Oklahoma Water Survey Director Jason Vogel and Ilona Peszlen, who teaches wood anatomy at North Carolina State University.
Feedback on a post-course survey was enthusiastic:
“This was a great, interesting course. Everyone in our group was interested in learning more.”
“Nice class. Very cool. I have told several people about it.”
“I liked the fact that I was able to learn a new skill in one day. And this skill can be used with simple inexpensive tools in the field.”
Bryan said that city officials in particular are increasingly concerned about erosion because sediment can pollute drinking water and choke culverts and bridges, contributing to flooding.
“We’re seeing a surge in the number of people using it,” he said of the innovative root analysis tool that he developed, turned into doctoral research and now is leading a Freese and Nichols team in applying.
“There’s not a better tool for quickly telling us what has happened” over the past five to 10 years, he said.
While dendrogeomophology had been used in Europe to study landslide and hillslope erosion, it wasn’t until the past decade that Bryan and his team adapted the technique for assessing river and streambank erosion in the United States.
The rings shown in a slice of root sample can reflect whether it was exposed rather than buried and for how long. Annual erosion rates can be calculated through a formula based on the root’s distance from the bank and years of exposure (as shown by the rings). This method takes less time than tracking erosion over multiple years; costs considerably less; and is similarly accurate to longer-term measurements. Basic skills can be taught to pipeline inspectors, interns and others who might be tasked with initial assessments.
Bryan said the procedure can help answer fundamental questions: How quickly is my streambank eroding? How much time do I have to act?
For example, in one city, Bryan and his team were able to show that a water intake was being clogged by erosion from a stream rather than a lake. In another instance, a new park was being blamed for stream erosion, but a dendrogeomophology analysis revealed that the problem predated development of the park.