NEWRY — Field work will finish this fall on a three-year brook trout ecology study in the Sunday River and Bear River watersheds.
In 2007, the Androscoggin Watershed Council, the Maine Department of Inland Fisheries and Wildlife, Newry, the University of Maine, Caribou Springs LLC of Gilead, Field Geology Services of Farmington, and the U.S. Fish and Wildlife Service partnered to try to restore habitat for native brookies and control erosion.
Coordinated by the council, the grant project was created to monitor the impacts of adding coarse woody material to streams.
If the experiment works as anticipated, it will be used more in western Maine to deal with massive erosion.
“We call it ‘chop and drop,’ because it involves cutting small trees at strategic intervals along streams,” project surveyor Jeff Stern said via e-mail on Thursday.
The trees fall into and across the water where they collect more material, like leaf litter.
In some spots, the technique may cause scouring to increase pool depth. In other places it might trap sediment to build bars.
“The hoped-for goals are to improve brook trout habitat and reduce erosion,” Stern said.
“Chop and drop is thought to mimic conditions that existed in Maine streams before logging, agriculture, land clearing and road building resulted in the tree-free streams we see today.”
Two streams in the upper Sunday River Watershed were treated with chop and drop in August 2007. A third stream there was left untreated to use as a control.
Two more sites — Branch and Chase Hill brooks in North Newry — were added in late 2008.
Last summer, Stern said he noticed that woody material was sorting itself out in the test streams.
“New pools and bars seemed to be much more defined than in previous years,” he said.
“The surveying and biomonitoring data for 2009 bore out these observations, especially up on the Sunday River tributaries. We might see even more dramatic results this year.”
Stern said the process seems to take two years before dramatic results are seen, like bar formation, sediment deposits, leaf litter and stick packing in the “dams,” pool scouring and sorting of wood into distinct debris jams.
“I also noticed stronger trends emerging in the (water level) logger data when comparing the upstream and downstream loggers,” he said.
“Now that the Sunday River sites are in their third year, and the Bear River sites are closing in on the two-year threshold since treatment, I anticipate the trends will continue and strengthen this year.”
Water loggers measure water pressure at 20-minute intervals inside a submerged “stilling well,” which the devices then convert to a water-level reading, Stern said.
Each test stream has a logger above and below the treated reach.
Readings are stored in the devices, which at season’s end are pulled from the stilling wells and their data uploaded into a computer in graph form.
A surveying company, Field Geology Services, then superimposes one graph atop the other to see whether chop and drop is moderating water level.
In downstream loggers, Stern said peak water levels after storms aren’t as high as they are above, while low levels downstream don’t sink quite as low as they do upstream.
“The theory is that chop and drop makes these notoriously ‘flashy’ streams less subject to wild fluctuations in water level by slowing water movement, and hence more stable for brook trout,” Stern said.
Flashiness, he added, results from past land uses like logging, agriculture, land clearing and road building.
This summer, project members will return to the sites to reinstall water-level loggers pulled in November from Sunday River tributaries and Chase Hill Brook.
They’ll also check data from one logger purposely left in Branch Brook.
“It will be interesting to see what the data from winter and spring runoff and recent rainstorms looks like,” Stern said. “We’ve never left loggers in before during the winter for fear of ice damage.”
This image shows, in blue outline at top left center, a “chop and drop” dam along a stream in the Sunday River Watershed in Newry that created a sand and gravel bar, at top right and outlined in red, behind the dam. Since 2007, Maine partners working on the Eastern Brook Trout Joint Venture project have been studying the effects of strategically felling small trees into streams where they collect leaf litter, reduce erosion and improve wild brookie habitat. Project field work ends this fall.