Renowned for its iconic monuments and history, the DC Region is also distinguished by its lush, verdant landscapes. Essential to that scenic beauty are the streams and watersheds that support our region’s ecological health and elevate the quality of life for all of us who live here.

Healthy streams are the lifeblood of our forests and green spaces, serving as precious habitats for a diverse range of flora and fauna. But our streams need our help!

The 2024 State of the Streams report is a unique snapshot of five important natural resources in our region: Accotink Creek, Little Falls Branch, Rock Creek, Seneca Creek, and Sligo Creek.

What makes this report so meaningful are the comprehensive criteria that measure the impacts on nature, people, climate resilience, and more. These criteria also point to why and how you can help make a positive difference in the health of local streams.

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Impervious surfaces are hard areas, like pavement, that don’t absorb water. High amounts of impervious surface means that water from rainfall picks up dirt and pollution and then flows into our streams.​

Being surrounded by as little as 30% of impervious surface significantly damages a stream. In our report, we found that all the streams studied, except for Rock Creek, were surrounded by at least 30% of impervious surface.

Benthic macroinvertebrates are organisms that spend part of their life cycle at the bottom of streams and rivers. These “Creek Critters” have varying tolerance levels for pollution and low oxygen. As a result, the presence of certain macroinvertebrates can help assess a stream’s health.

(Learn more by downloading our free Creek Critters app)

Like benthic macroinvertebrates, the types of fish populations that thrive in a stream are another measure of overall health.

This metric is also called the Fish Index of Biotic Integrity or FIBI.

Water chemistry is an evaluation of various elements conducive to supporting healthy plants and animals in a stream.​

Although there are a wide variety of factors that can be measured in water chemistry, this report focused on each stream’s temperature, pH, dissolved oxygen levels, and specific conductivity.

Even with clean water and plenty of food, some fish populations can still suffer if conditions prevent them from swimming freely through a stream. Obstacles like dams, waterfalls, and sewer line blockages are identified as part of a fish passage indicator or stream blockages.

Invasive plants can spread quickly through a habitat monopolizing resources but offering little or no benefit in return. Invasives compete for water, soil nutrients, and space, but because they are typically non-native to the region, native birds and wildlife won’t or can’t eat them.

The Physical Benthic Habitat Index measures the physical habitat of a stream. Important factors that influence this habitat are water flow, erosion, and the streambed or substrate. These all affect how suitable a stream habitat is for various organisms.

Like fish and benthic macroinvertebrates, birds are another excellent indicator of stream health. Data on birds was collected by identifying the species that reside along each stream. Each stream plays host to many species of native and migratory birds at least somewhere in the watershed.

Tree canopy is a measure of the percentage of land that is shaded by trees. A dense tree canopy protects a stream from being degraded by invasive plants, urban development, and climate change.

People living in communities with a dense tree canopy enjoy protection from extreme heat, reduced air pollution and flooding, and lower electric bills for cooling homes and buildings.

Air quality is a measurement of the pollution in the air we breathe – everything from pollutants like vehicle emissions or gas stoves to climate disasters like smoke from wildfires. Trees help clean our air but they can’t do it all.​ Air monitoring stations collect air quality data mainly used by government agencies. No monitoring stations are located within the watersheds in this report, so the scores reflect data from monitoring stations closest to each stream. ​

Stream buffer (or riparian buffer) describes the plants and trees that grow along a stream or river. That buffer is critical to a stream’s ecosystem in many ways. ​A robust buffer regulates stream temperatures to protect fish, benthic macroinvertebrates, and other wildlife from the warming temperatures of climate change. Healthy stream buffers also protect stream banks from erosion caused by more intense storms.

A wetland is land covered by or saturated with water at all times or during certain seasons in the year. Swamps and marshes are common examples. Wetlands mitigate many of the effects of climate change by providing habitat for animals, reducing flooding by holding excess water, and storing greenhouse gases.

Trees are crucial for a healthy ecosystem, as well as human health, environment, and economies. Biased land use policies, redlining, and racial covenants have resulted in many low-income neighborhoods and neighborhoods of color having fewer trees. This worsens issues like air pollution, oppressive heat, flooding, public health, and even crime. ​The American Forests’ Tree Equity Score helped us score this metric.

Access to green space (most often in the form of parks in urban areas) is vital to supporting human health and resilient communities. Park access, according to The National Recreation and Park Association (NRPA), is the “just and fair quantity, proximity and connections to quality parks and green space, recreation facilities, as well as programs that are safe, inclusive, culturally relevant and welcoming to everyone.”