What its tiniest residents tell us about Broad Branch Stream’s health

by Sarah Becker

Tucked away in the Forest Hills community flows the recently restored Broad Branch stream. At first glance one would not assume that just a few years ago the stream was “daylighted” and freed from the pipe where it had been confined for years.

With the help of additional stewardship after the initial restoration ended, the area has matured and reestablished itself as a part of the community and the ecosystem.

Dani Churchill, a habitat restoration and urban forestry intern with the Rock Creek Conservancy, has been leading stewardship in the area this summer. For her, maintaining the integrity of the restoration consists of watering newly planted native grasses, perennials, and trees, as well as removing invasives throughout the over six-acre swath of land. Both activities encourage the establishment of native plants, which in turn clean and filter stormwater runoff before it even enters the stream.

Dani has also worked with volunteers from the neighborhoods and from local businesses to keep the restoration clean, and to improve the aesthetic appeal of the area. The stewardship activities build upon the investment that went into the initial restoration, and are ensuring its success.

While some signs of the stream’s improving health are evident – the surrounding greenery, tadpoles, and other wildlife are thriving – other indicators are not quite so apparent. Dani and I visited the stream on August 8th to look at benthic macroinvertebrates, the small organisms that cling to the rocky streambed and reflect the true health of Broad Branch. Since the stream had been covered until 2015, the macroinvertebrate population has had relatively little time to establish itself. However, it is apparent that a macroinvertebrate community is starting to take hold.

During our collection we found seven different macroinvertebrates.

• Pouch snail
• Black fly larva
• Leech
• Common netspinner caddisfly
• Midge fly larva
• Narrowwinged damselfly
• Darner dragonfly larva

These organisms exhibit different levels of sensitivity to pollution, so the presence of specific types can help tell us about stream health. We used the Audubon Naturalist Society’s “Creek Critters” app to identify and list the macroinvertebrates, and to generate a stream health report based on our findings. Most of those we found have relatively high pollution tolerances.

Due to the relatively low diversity and high tolerances, “Creek Critters” assessed the water quality in Broad Branch as “fair.” Although a rating of “fair” may initially seem discouraging, we were excited to find dragonfly, damselfly, and caddisfly larvae which indicate the restoration project is not only helping protect Rock Creek by controlling stormwater runoff, but also tells the story of the revival of the biotic community. Ongoing stewardship and neighborhood actions to reduce polluted runoff will help other macroinvertebrate species take hold, boosting the stream’s health even more.

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Sarah Becker is a summer intern with the Audubon Naturalist Society.
Dani Churchill is a summer intern with the Rock Creek Conservancy.

Interested in learning more about stream macroinvertebrates? Download the free ANS “Creek Critters” app from the Apple App Store or Google Play. Also, the Audubon Naturalist Society is offers stream science classes and field study workshops. For more information, please visit anshome.org/water-quality-monitoring.