CRJC Brings State-of-the-Art River Restoration to Colebrook

Colebrook has a well-earned reputation as the can-do town of the North Country, and will soon have more – very dramatic – proof. As soon as a certain signed letter arrives from Washington, the Connecticut River Joint Commissions will start work on a major new installation at the Colebrook Business Park - the first of its kind in the eastern United States. Six engineered log jams will be built to stabilize the swiftly eroding riverbank. Last fall, CRJC restored the lowermost Mohawk River to treat the cause of the erosion: artificial straightening in the 1960s by the US Army Corps of Engineers.

CRJC and Dr. John Field have been working with the Town and the Colebrook Development Corporation for six years to design and raise funds for the project. The missing final piece is a federal Economic Development Administration Grant. During the last year, while CRJC has waited for written approval, the Park has lost approximately 30 more feet of riverbank. Once funding is approved, bids for construction to EDA specifications must be issued. Construction will hopefully begin in mid summer, and will take up to six weeks. CRJC stabilized 600 feet of an adjacent lower bank in 2006 using root wads and a riparian buffer planting.

Purpose of Project

  • To protect water quality and fish habitat by protecting the riverbank at the Business Park from erosion.
  • To remove the cause of the erosion by correcting a human error in altering the lower Mohawk River.
  • To demonstrate a new, science-based, river- and fish-friendly approach to riverbank restoration that mimics nature and uses natural local materials.

Project Design - The project has two interrelated parts: returning the lower Mohawk River to its natural path, and stabilizing the Business Park.

  • Business Park - install six engineered log jams, using a large number of trees, some with their root systems still attached. Each jam is a carefully designed, multi-layered, interlocking box structure, at the river's edge, to force the current away from the bank. Plant native trees and shrubs to further stabilize the log jams and provide shade to keep water cool for trout.
  • Lower Mohawk River - install several smaller log jams to divert water back into old abandoned channels, to help catch gravel and other sediment and keep it out of the mainstem Connecticut where it causes erosion at the business park. This work is now complete.
  • Engineered log jams have been successfully used in the American Pacific Northwest, where they have helped protect major highways in situations where rock riprap had repeatedly failed. The log jams are also being extensively used on trout rivers in Australia. The structures will mimic natural log jams and log cribs from logging booms.
  • Rock riprap is the wrong choice for this site for many reasons: the deep hole offshore prevents installing rock in a way that will hold; rock would destroy fish habitat; rock would create new erosion problems nearby; permits and funding could not be secured for this approach.

Background

  • 2004 - CRJC's geomorphic assessment of 85 miles of the Connecticut River, by Dr. John Field, identified the problem at the Business Park and its cause, gravel and other sediment coming from the straightened lower Mohawk River. When the Connecticut is forced to flow around the large gravel bars, its current is directed at the Business Park riverbank.
  • 2005 - CRJC then applied for funding to address this.
  • 2006 - CRJC installed 600 feet of root wads and riparian buffer (riverbank plantings of native trees and shrubs) at the lower end of the Business Park property, hoping to restore the rest of the park's riverbank the next year (the higher bank requires a more complicated solution because of a deep hole just offshore)
  • 2007 - CRJC sponsored Dr. Field's study of the Mohawk River, to evaluate whether restoring the lower channel near the wastewater treatment plant would affect downtown Colebrook; learned it would not. (This project is downstream of and not related to the failing retaining wall near Colebrook Academy)
  • 2007 - Colebrook Development Corporation and Business Park landowners donated a conservation easement on the Business Park shoreline to the Town. Much of this shoreline has since disappeared downriver.
  • 2008 - CRJC sponsored engineering studies on that part of the Business Park that was still eroding, and created a design that includes large constructed log jams. CRJC also won a number of grants to cover many of the costs.
  • July, 2008 - Governor Lynch viewed the riverbank with CRJC and DES staff. By September, the riverbank upon which they stood had washed away.
  • April, 2009 - NH Department of Environmental Services encouraged North Country Council, an essential partner, to assist Colebrook in applying for an Economic Development Administration grant for the remaining funds needed for the Business Park part of the project. Currently waiting for approval.
  • November, 2009 - CRJC completed restoration of the lower Mohawk River by installing log diversions and engineered log jams to direct flow back into the historic alluvial fan.
  • The Town of Colebrook has been an active and essential partner, especially through Public Works Director Kevin McKinnon and Selectman Larry Rappaport, Colebrook's representatives to CRJC's Headwaters Subcommittee.
  • NH DES has been very supportive and has issued a permit for both parts of the project.
  • CRJC's Technical Advisory Committee for the project has included staff from USDA Natural Resources Conservation Service, NH DES, and NH Fish and Game.

Funding Summary - CRJC has raised a total of $525,872 for the project:

  • NH Department of Environmental Services, Clean Water Act funding: $147,744
  • NH Fish and Game Department: $30,000
  • NH Moose Plate Program (conservation license plate): $61,000
  • Upper Connecticut River Mitigation & Enhancement Fund: $185,128
  • Neil & Louise Tillotson Fund: $60,000
  • EPA funding through the Connecticut River Tri-State Targeted Watershed Initiative: $10,000
  • Town of Colebrook will contribute $30,000 worth of trucking
  • be raised from federal Economic Development Administration: $508,640

Partners

  • Town of Colebrook - will place a conservation easement on town land between the wastewater treatment plant, the Mohawk River, and the Connecticut (a condition of one of the grants).
  • North Country Council - assisting Colebrook with grant application and administration.
  • Volunteers from Colebrook Academy and CRJC's Headwaters Subcommittee - will help with monitoring plantings
  • Colebrook Development Corporation and riverbank landowners
  • NH DES
  • NH Fish & Game

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Bank Stabilization Implementation and Assessment of the Connecticut River near Colebrook (and Groveton), NH, 2006

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