Every spring and sometimes in the summer, the Cold River would take a bite out of two important agricultural fields near its confluence with the Connecticut River in Walpole. Overtime, this constant nibbling was really starting to add up. Nearly an acre of some of the most productive farm soils in the United States were lost to this process in the last 15 years.
About three years ago, landowners on both sides of the river approached the USDA’s Natural Resource Conservation Service to see what could be done to protect their fields from this ongoing damage, and set in motion a complex project that will be completed later this month.
Before it was completed, the project, located just downstream of the Route 123 bridge over the Cold River, involved dozens of people from many organizations. Working together, the NH Association of Conservation Districts, the Cheshire County Conservation District, the Monadnock Conservancy, the Connecticut River Conservancy, two landowners, two farmers who work the fields, several state and local agencies, engineers, and private contractors from as far away as Maine, a plan was developed to use biomimicry to help keep the river in its banks, and to help keep the banks where they are now.
The system consists of two major pieces: a series of log jam revetments that armor the banks and dissipate the energy of water and ice flowing down the river, and a buffer strip of native riparian trees and shrubs to hold the soil in place with their complex root systems.
Trees and shrubs have been planted on the north side of the river, and are scheduled to be planted on the south side later this month.
As a bonus, the log jam structures serve as shelter for fish and as perches for birds that hunt fish and insects in and above the water surface. The riparian buffer will also provide habitat for birds and mammals, and may help to keep the water in the Cold River just a little bit cooler when the trees grow and start to provide some shade.
Just as important, the whole system will reduce the major erosion that has been happening on the site every year, sending sediment, soil nutrients, and irreplaceable topsoil down the Connecticut River to the Long Island Sound estuary.
If you drove past the site earlier this summer and saw the huge piles of trees with the root wads still attached, and lots of big machines, that’s what it was all about.
Written by Bill Fosher
Owner, Edgefield Farm
Conservation Planner, NHACD
Image by Nancy Bryant Photography