Water Science and Restoration
Restoration: Stream Continuity and Healthy Streambanks
The healthiest rivers tend to be free flowing with vegetated streambanks, ideally permanently protected greenways. A variety of impediments can negatively impact stream continuity, including obsolete man-made dams and improperly size and sited culverts. Such features alter the flow of the water and can prevent free movement of aquatic wildlife. Water quality and aquatic habitat are also degraded by polluted runoff and erosion where riverbanks lack vegetation. Water temperatures may rise to unhealthy levels where streamside shrub and tree cover is lacking.
US EPA
Stream Continuity
Restoring stream continuity, the natural connection and unimpeded flow of a waterway, is a major focus of the NRWA. Stream continuity improves water quality and aquatic habitat, allows natural movement of stream sediments, and helps to alleivate the impacts of climate change.
Dam Removals and Ecological Restoration
Aging, obsolete dams are major obstacles for aquatic wildlife such as fish and turtles, limiting their movement up and downstream in their environment. Impoundments of water behind dams cause warmer water temperatures and encourage invasive plant species to grow impacting the diversity of wildlife that will find adequate habitat there. Additionally, as our climate continues to change and we experience more extreme weather events, these dams present a threat to human health from flooding or breach. Upkeep and maintenance of these dams is an expensive undertaking for responsible municipalities, businesses, and individuals. NRWA works with municipalities, state agencies, and conservation partners to consider dam removal, where appropriate, supporting grant efforts and ecological restoration after removal. See our current projects below.
Culvert Assessments
Inappropriately sized or sited stream culverts also inhibit stream flow and wildlife movement, and can risk destruction of infrastructure during heavy rainstorms. Many of our existing culverts were designed decades ago and they are no longer suited in size for our new rainfall trends. Older culverts can also be sited or degraded so that they now sit above normal or low stream flow, essentially blocking water and animal movement. NRWA staff are certified by North Atlantic Aquatic Connectivity Collaborative (NAACC) to conduct assessments of culverts, and have assessed culverts for many municipalities throughout the watershed. NRWA also offers training opportunities for municipal and state officials, conservation organization staff, and environmental consultants to become NAACC certified. Assessments can help communities develop a list of prioritized culvert redesign/repair projects and position them to receive state grant funding. See our current projects below.
Old undersized and poorly sited culverts can become scoured by flooding from excessive rain events leading to the disruption of stream continuity as the culvert now sits above the stream level which prevents movement of fish and other aquatic species.
Healthy Streambanks
Well vegetated streambanks serve as riparian buffers filtering polluted runoff before it enters the waterway. The root systems help to stabilize the banks preventing erosion and silting. Shrubs and trees provide shade reducing water temperatures for cold water fish, and provide food and habitat for a diversity of species. The NRWA is working to restore riparian buffers through a project managed by the Merrimack River Watershed Council with funding from the USDA. Working with local communities and volunteers, the NRWA identifies sites in need of restoration, and conducts workdays to remove invasive plant species and plant native species to provide healthy streambank vegetation and wildlife habitat. NRWA also advocates for permanently protected greenways through its Marion Stoddart Greenway Protection Plan.
