Science Insights
A standard approach to monitoring dam removal
By Peter H. Taylor

Almost every day, when I am driving around the Maine town where I live, I cross a bridge over the Royal River. It is a scenic river about 150 feet (46 meters) wide that drains an area of 365 square kilometers (141 square miles) into Casco Bay. For more than a century, the river was the town’s lifeblood. Dams powered mills that provided jobs for hundreds of people.

Today, the Royal River has lost its prominence in the local economy. The mills are mostly gone, and the town has become a quiet, residential suburb. Now people mainly value the river as a scenic feature and a place for recreation. It no longer provides many jobs. But the dams are still here, impeding the flow of water from uplands to the sea.

When I am driving across the river, I usually glance downstream at one of the dams. I muse about the fish that cannot migrate because of it and the other lost connections between land and sea. These dams are such longstanding elements of the local scene, and seem so integral to the place, that it is easy to forget they were not always here. Except for the last few hundred years — a blip in geological time — the Royal River flowed free. How would the ecosystem respond if its dams were removed?

Covering 179,000 square kilometers (69,000 square miles), the Gulf of Maine’s watershed encompasses the entire state of Maine and parts of New Hampshire, Massachusetts, Nova Scotia, New Brunswick and Quebec. The Royal River is one of many rivers that drain water from this land area into the Gulf. It has two dams, according to the Inventory of Potential Habitat Restoration Sites (http://restoration.gulfofmaine.org/nea/search.php).

The number of dams on these rivers is astounding. Rivers in the U.S. portion alone of the Gulf of Maine’s watershed have more than 4,800 dams. State inventories found 2,506 dams in New Hampshire, 782 in Maine and 1,579 in Massachusetts. (Inventories varied in comprehensiveness, and Maine undoubtedly has many more than 782 dams.) Many of these dams are aging and are no longer needed, but they continue standing as relics.

While the Royal River is no longer the economic lifeblood of my town, it continues to be — just as it always has been — a critical part of the ecosystem. The freshwater ecosystem of the river itself connects intimately in innumerable ways with the surrounding terrestrial ecosystem and the marine ecosystem into which it flows. Like plaques clogging an artery, the dams on the Royal River impair the health of the river and, in turn, the larger ecosystem.

Recognizing that removing dams can benefit the ecosystem, the economy and public safety, government agencies, non-government organizations and private parties have demolished some 600 dams throughout the United States in recent decades. Some 20 dams have been taken down in the U.S. portion of the Gulf of Maine’s watershed since 1995, and 20 more are being considered for removal.

These projects require tremendous investments in time and money, and sometimes they are contentious because of the socioeconomic significance of dam removal. It makes sense that ecological changes should be monitored afterwards to determine if the goals were accomplished and to learn the best ways to conduct dam removals. For most dam removals, however, little information is collected about the riverbed, wildlife and habitats. When monitoring does occur, the methods vary tremendously, making it difficult to compare outcomes of different dam removals. We know far less than we should about how the ecosystem responds after a dam is removed.

An initiative led by the River Restoration Monitoring Steering Committee of the Gulf of Maine Council on the Marine Environment is addressing this knowledge gap. Working with more than 70 scientists, resource managers and watershed restoration practitioners from around the Gulf of Maine, the Steering Committee has developed a standardized approach to environmental monitoring of dam removal sites. According to a document produced by the Steering Committee with assistance from the New Hampshire Coastal Program, if this approach is adopted scientists should be able to:

• evaluate the performance of individual habitat restoration projects;
• assess the long-term ecological response of regional restoration efforts;
• advance our understanding of restoration ecology and improve restoration techniques;
• better anticipate the effects of future stream barrier removal projects; and
• communicate monitoring results to stakeholders and the public.

In this standardized approach, the Steering Committee has identified eight critical monitoring parameters for every dam removal site: monumented cross sections, longitudinal stream profiles, stream bed sediment grain size distribution, photo stations, water quality, riparian plant community structure, macroinvertebrates and fish passage assessment. A forthcoming guide produced by the Steering Committee in collaboration with the Gulf of Maine Science Translation Project and the New Hampshire Coastal Program will present the rationale and methods for using these parameters. Release of the monitoring guide will be announced on the Gulf of Maine Council’s Web site (http://www.gulfofmaine.org/).

Perhaps one day, as I drive across the Royal River, I will glance downstream at where a dam used to be and see a group of scientists wading in the water, using these standardized monitoring methods. Then I can find out how the ecosystem responds to the river flowing free again.

Peter H. Taylor is a consultant (http://www.waterviewconsulting.com/) for the Gulf of Maine Science Translation Project.

The online Inventory of Potential Habitat Restoration Sites (http://restoration.gulfofmaine.org/nea/search.php/) provides information, photos and maps of dams and other human impacts on the Royal River and three other rivers that flow into the Gulf of Maine. Or, explore the sites on an interactive map (http://www.gulfofmaine.org/maps/hrp/htdocs/index.html?map=nea).

© 2007 The Gulf of Maine Times