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Helping Streams Help Themselves, Naturally

The sights and sounds of a stream running through your backyard or your favorite neighborhood park can be a soothing antidote to the busy pace of modern life.  But when U.S. Environmental Protection Agency scientists Paul Mayer and Elise Striz look at a creek bed, they notice something that nature hadn’t intended. They observe the negative effects of water running off the paved surfaces of the urban landscape.

“Water runoff is changing the flow of many streams,” says Paul Mayer, Ecologist, U.S. EPA Groundwater and Ecosystem Restoration Division, or GWERD.  “Rapid runoff of rain from pavement causes stream banks to erode and forces streams to move laterally in ways that are impacting people’s homes, exposing water and sewer lines, and negatively impacting both ground and surface water quality.”

The shifting streams are a problem for municipalities like the Baltimore County Department of Environmental Protection and Resource Management, which is working collaboratively with Mayer and his colleagues at GWERD.  Not only are the streams encroaching on private property and jeopardizing the urban infrastructure, the water runoff functions as a delivery system for excess nitrogen into the stream bed.

A little bit of nitrogen is necessary for the growth of all living things, but too much nitrogen can be bad for humans and the environment.  Too much nitrogen in drinking water can negatively affect human health and too much nitrogen in streams can impact the ecological health of nearby watersheds and estuaries.

“The nitrogen is coming from many sources,” says Elise Striz, Hydrologist, also at GWERD. She says those sources include “excess fertilizer runoff, animal wastes, sewer lines, and even the byproduct of fossil fuel combustion from your automobile’s exhaust.” 

The solution to excess nitrogen may well lie in the same method used to protect the streams from erosion – stream restoration.

“It is an engineered approach to land management that redirects the flow of the stream,” says Mayer.  “By reconstructing the natural twists, turns and bumps of the stream, and re-establishing plant communities along the stream banks, stream restoration may not only address the land management problems but also improve water quality at the same time.”

Mayer and Striz have been testing this theory in a real-world experiment in an urban stream named Minebank Run in Towson, Maryland, outside of Baltimore. Minebank Run had become degraded in recent years, suffering from erosion, sediment buildup, and the loss of plants and trees along the stream banks. The belief is that by restoring the stream, scientists will be able to simultaneously recreate the conditions necessary for natural nitrogen removal from the stream. The result would be a cost-effective, sustainable method for keeping streams vibrant, which in turn aids the health of their plant, animal and human neighbors as well as downstream waterways, such as the Chesapeake Bay.

“Naturally existing bacteria actually transform the nitrogen and can reduce the nitrogen level in the water in a dramatic way,” says Mayer. “So, the goal is to create a healthy stream environment within which these natural bacteria can thrive.”

In order to test the effectiveness of this natural nitrogen removal, Mayer has been comparing nitrogen levels in Minebank Run from before and after its restoration. The early results have been impressive. Mayer says the natural features of the stream bed have been greatly improved since restoration. There is far less erosion of the stream, more plant life growing on the stream banks and, as anticipated, excess nitrogen is naturally being removed from the stream and the ground water beneath it.

In short: by restoring the stream bed back to a more natural state, the stream itself can provide cleaner water for the plants, animals, and humans that rely on the stream. More study is certainly needed. But you can be sure that Mayer, Striz and their colleagues are doing just that, keeping their eyes and ears open.

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