An Examination of Impervious Cover, Stream Restoration and Ecosystem Response
Berry Brook, Dover, NH
Location: Berry Brook is a small 185 acre watershed in Dover NH. Berry Brook itself is 0.9 miles long and flows through the heart of central Dover eventually ending at the Cocheco River at Sixth Street. The brook collects water from approximately 185 acres that surround the brook.
Issue: Water pollution.
What kind of pollution? What is the cause?
According to clean water standards from the EPA (US Environmental Protection Agency), Berry Brook has a very low population of aquatic insects that are normally present in clean water. The brook is also polluted by high amounts of E.coli (fecal) bacteria during heavy rain events.
The pollution in the brook seems to be related to storm run-off from the high amount of developed area (streets, sidewalks, parking lots, roofs, lawns) relative to natural areas, such as forest, wetland, or fields. This run-off contains nutrients (such as excess lawn fertilizer, dog poop, and smog-related pollution), heavy metals and oil from automobiles, and road salt.
How do we fix it?
- Reduce the amount of run-off that reaches the brook untreated. Much of the pollution problem is caused when untreated run-off from streets and other hard surfaces goes straight into the brook from storm drains. If run-off can be diverted away from storm drains and into gardens and naturally forested areas, it can pass into and through the soil. When it reaches the brook through ground water, it is much cleaner. It also reaches the brook more slowly, so flooding and erosion issues are lessened.
- Return the brook to its natural flow. The waterworks off Roosevelt Ave. hid the brook under ground in the former water reservoir. The brook has been brought back into the light of day and engineers have tried to copy the path of what its natural flow might have been. Trees, shrubs, and other native plants have been planted to hold the soil, provide shade, and help filter run-off. Engineers have also installed a wetland area in the waterworks area. This will help hold extra water, increase the amount of water that is filtered through natural soils, and slowly release water to the brook when rainfall is low.
What has happened already?
To date over 18 projects have been completed reducing the effective impervious cover in the watershed from 30% down to 15%.
Find a map of all the current and future installations and a short description of the work here: BB installation summary
What will be happening in the next year?
- Install more natural areas to collect rain and recreate wildlife areas in the lower stream.
- Adjust the stream channel near Sixth Street to reduce flooding.
- Develop low-impact public trails and walking bridges.
- Monitor stream water for improvements.
When can we expect the water to be clean?
That’s a big question. Berry Brook has been suffering for a long time. The process of bringing the brook back into daylight disturbed a lot of soil. Although that soil has been planted with trees and other soil-holding plants, the plants are very young and have not yet developed good, deep roots. Heavy storms always carry a risk of erosion, and erosion of soil adds nutrients. The sources of pollution, run-off and fecal matter, will probably continue to be present if neighbors do not help to reduce them. If neighbors do their part to reduce pollution, the water will be cleaner sooner. Results of modeled estimates of pollutant load reductions are presented in the table below:
For more results from the project you can download the following pdf summary: Berry Brook Results
Who is doing and paying for this work?
This project is a partnership among the City of Dover, the University of New Hampshire Stormwater Center, the Cocheco River Watershed Coalition, the New Hampshire Fish and Game Department, American Rivers, and the New Hampshire Department of Environmental Services. Funding is provided through a series of grants from the NH Dept. of Environmental Services and matching funding from the City of Dover.
What can I do to help?
- Get involved!
- Pick up dog poop and dispose of it properly in the garbage.
- Dispose of cat litter in the garbage.
- Discourage dogs and children from playing on or near stream banks to help reduce erosion. Keep stream banks natural with trees and shrubs.
- Keep automobiles well maintained. Fix fluid leaks promptly.
- Never dump anything down a storm drain.
- Minimize or eliminate the use of lawn fertilizer and pesticides.
- Reduce the amount of salt placed on driveways and sidewalks.
Funding for this project was provided in part by a Watershed Assistance Grant from the NH Department of Environmental Services with Clean Water Act Section 319 funds from the U.S. Environmental Protection Agency and funding from the Great Bay Stewards.