This fall, a half-mile stretch of the Pomperaug River that flows through the Audubon at the Bent of the River (BOTR) in Southbury was the site of a highly successful project to restore in-stream habitat. Decades ago this stretch of the River was channelized causing significant changes to the natural flow which greatly reduced habitat diversity. The recent improvements introduced large woody debris to the stream environment in effort to recreate that pools, riffles and glides that once characterized the area.
Leslie MacLise-Kane, Center Director at BOTR, said, “Trout and other aquatic species rely on a variety of other flow patterns for feeding, finding shelter, and for spawning. Our goal was to restore the river to a more natural ecosystem that will benefit all species.”
Jim Drennan, Habitat Manager at BOTR, explained that large woody debris (LWD) in a river helps create pools that provide hiding and resting places for fish, especially during low streamflow. It can also help create scour pockets or holes that provide fish with shelter in heavier flows. He noted that, “We are already seeing the woody debris accumulate wood, leaves, and organic material on the upstream side of the ‘structures’ and sediment scour below them. It’s gratifying to see how the structures we have installed add so quickly to the complexity and diversity of the stream channel.”
“We have also observed evidence of many animals feeding on and around the in-stream structures. We have a great blue heron who has taken up residence on one particular structure as well as kingfisher darting along from structure to structure up and down the river” MacLise-Kane added. She went on to note that “the structures and streambank also held up quite well during the high water conditions we experienced just after installation. Not only is this a testament to the engineer and construction team, it underscores the benefit LWD can have in absorbing what might be highly erosive currents.”
The project was made possible by a grant from the 2010 Ecosystem Management and Long Island Sound Fund, awarded by the Connecticut Department of Energy and Environmental Protection (CT DEEP). Don Mysling, Senior Fisheries Biologist from CT DEEP Inland Fisheries Division said, “I am pleased that this project has been completed. It is a project well done and demonstrates what can be accomplished with the cooperation of a number of interested partners!”
The project was conceptualized by Audubon BOTR and Pomperaug River Watershed Coalition (PRWC) as a restorative measure to return the resident fish population to one that is consistent with the “reference fish community” – what should be found for a river with similar climate, geology, size, and flow. Carol Haskins, Outreach Director at PRWC noted, “The project proposal drew heavily on scientific research about the habitat availability of the Pomperaug River completed by Rushing Rivers Institute for PRWC.”
Laura Wildman of Princeton Hydrology, a New Jersey based firm, served as Project Engineer and designed ten separate structures to be installed in the half-mile stretch of the Pomperaug River. Wildman noted that, “Constructed LWD projects are designed to not block the channel, only partially extend into the channel adding habitat and complexity to the river. They are not intended to act as a dam or to block navigation.” ” Dale Bentz of River Logic, a Pennsylvania based company, completed the construction and installation.
To further measure the success of the project, a post-construction fish assemblage survey will be completed during the 2014 field season. The survey data will be compared to the pre-construction survey completed in June 2012 and to the reference fish community. A presentation about the project and tour of the project site is being planned for Summer 2014. For more information, contact Audubon at Bent of the River at 203-264-5098 or visit their website, http://bentoftheriver.audubon.org/.
PHOTO CAPTION: Dale Bentz of River Logic carefully moves trees and other large pieces of woody debris in a half-mile stretch Pomperaug River to create ten “constructed log jams” that were designed by Laura Wildman of Princeton Hydrology. The goal of the project, which took place at the Audubon Center at Bent of the River in Southbury, was to recreate that pools, riffles and glides that once characterized the area and restore the river to a more natural ecosystem that will benefit all species.