It is not often that a storm as powerful as Tropical Storm Irene blows through western Massachusetts, and assistant geoscience professor Jonathan Woodruff and graduate student Laura Kratz were determined to take advantage of it.
So, the duo took to the Connecticut River in canoes to study how major storms impact the movement of sediment in the river.
Two days before the storm, Woodruff took baseline samples from the Oxbow in Northampton to Long Island Sound. Then, two weeks after the storm Kratz along with teams of students took new samples.
“Irene presented the unique opportunity to see how sedimentation and contaminant levels in different depositional environments changed in response to a really big event, compared to the samples already collected for after more moderate flooding in the spring,” said Woodruff.
Storms as large as Irene are rare and the amount of sediment that was shaken up by the storm was much more than anything previously recorded according to Kratz. The flooding in Vermont, which represents the upper watershed, was a significant contributor to the sediment movement.
The samples showed that at most sites Tropical Storm Irene deposited as much as twice the amount of sediment, according to Kratz. This sediment also helped to clean up contaminants within the river.
“The strength of the floodwaters in the upper watershed scoured this sediment and transported it down to the lower watershed, where it covered sediment that is contaminated with mercury from the valley’s legacy of industry,” said Kratz. “The sediment from Irene is ‘cleaner’ or less contaminated with mercury, than the underlying sediment, so the storm served to cap the mercury.”
The samples were taken by lowering a tube off the side of a canoe and hauling it along the bottom to collect sediment according to to Kratz. Most of these samples were taken in coves.
“Working on a floating, rocking workspace was tough at first, but everyone quickly adapted,” said Kratz. “It was an excellent exercise in teamwork, communication and coordination.”
While previous research has illustrated what factors govern how sediment is deposited during flooding events, thus far research has not been done on the differences in manmade versus natural coves, according to Kratz.
“This research aims to fill that gap,” she said.
The research is part of a larger project of Woodruff’s.
“We have a larger project looking at how sediments and associated contaminants have been distributed along the lower Connecticut River since the onset of industrialization,” said Woodruff.
Irene offered an opportunity to compare large flooding events to the minor annual flooding that happens annually in the spring, called the Spring Freshet.
The study was paid for by a a one-year, approximately $21,000 “rapid response” research grant from the National Science Foundation. The findings will be presented at the Geological Society of America’s Northeast Division annual meeting in March.
Katie Landeck can be reached at [email protected].
