Studying Stream Restoration

By Marguerite Huber

Stream running through a lush, forested landscape

Forested stream

When I was younger, there was a prairie and stream behind my house. I ran and played there all the time with my friends until a house was built in its place. The lot was transformed from a wild, overgrown landscape to a manicured lawn. With the prairie gone and stream no longer enticing our adventures, we stopped playing there.

When homes and roads are built, they affect the habitat, quantity, and quality of water in downstream ecosystems (as well as natural places for kids to play!). Additionally, it causes an increase in nutrients like the fertilizer from that manicured lawn, and sediments, metals, and other pollutants making development a leading factor in stream impairment.

Local communities are increasingly turning to engineered techniques intended to reduce or eliminate the impacts of development on streams and other aquatic ecosystems. But do such efforts work?

Stream running through an urban area

Urban stream

EPA scientists Naomi Detenbeck and Nathan Smucker set out to evaluate how well “out-of-stream” restoration actions (those actions that take place in the watershed as opposed to within streams) work and to identify any general trends found in the scientific literature. They examined the response of water quality, habitat and hydrology, and ecological structure and function to development and restoration.

The scientists used statistical analysis to identify more than 40-years’ worth of published scientific literature on effective ways to protect streams from the unintended impacts of activities that harm streams. Starting with more than 1,400 papers, they pared it down to thirty-eight that covered forty-four restoration projects.

Smucker and Detenbeck found that the projects covered a number of stream restoration actions such as riparian buffers, human-made wetlands, and stormwater ponds. The projects looked at the bigger picture of managing streams by focusing on their watersheds. These “out-of-stream” approaches are important because efforts that have focused solely on habitat restoration within streams have had limited success.

Pooling together data from all the papers, the researchers found that biodiversity was reduced by more than half in unrestored urban streams and measures of things such as reducing erosion, nitrogen fixation, and other ecosystems services were significantly greater in restored streams than unrestored.

Even if it is impossible to fully restore streams, preventative actions can still be taken to protect downstream ecosystems in watersheds that are facing future development. In addition, tracking restoration projects (like the ones used in the studies) and ongoing monitoring would benefit future efforts to protect, restore, and manage streams.

Knowing what works and what doesn’t can help government agencies, policymakers, and citizens recognize and evaluate potential environmental outcomes resulting from their actions and decisions. It can also aid in setting restoration goals, prioritizing sites to monitor, and guiding future decisions and development as populations continue to grow.

About the Author: Marguerite Huber is a student contractor with EPA’s Science Communications Team.