The Anacostia River watershed is identified as one of three Areas of Concern by the Chesapeake Bay Program and listed as one of the most impaired rivers in North America by American Rivers, Inc. The challenge: restore the Anacostia watershed beginning with its tributaries.
Like capillaries transporting precious oxygen throughout a body, streams are the lifeblood to a watershed. But they can also carry pollutants, often land-based, that can harm the native fish and wildlife.
The job of cleaning and restoring the Anacostia River and its tributaries is a daunting task. Activities like removing trash from rivers, patching eroding banks or planting trees along streams may help by treating some of the symptoms. But to improve aquatic systems enough to support thriving communities of fish and other wildlife, a holistic approach is needed.
The U.S. Fish and Wildlife Service, Chesapeake Bay Field Office and the District of Columbia, Department of Health, Watershed Protection Division formed a partnership to take on this challenge, starting first with the restoration of Watts Branch, a tributary to the Anacostia. This restoration is critical to the restoration of the Anacostia River.
A watershed restoration approach involves the assessment of the stream and its watershed to show a cause and effect relationship between watershed land activities and stream processes. The physical features of the streams, such as channel dimension, pattern and profile, are characterized and the stability conditions assessed. Watershed characteristics such as land use, land cover, soil types, hydrology, topography and geology are also documented. Using historical maps and aerial photos, the Service can also develop an understanding of how a stream responds to certain land changes over time.
Restoration activities are then prioritized based on the severity, complexity, and scale of stream problems and the potential for the stream to recover on its own. Other factors such as community concerns, watershed restoration needs or habitat improvements also play a role.
The Watts Branch assessment showed conditions typically found in an urban environment. Conversion of tributaries to piped or concrete-lined storm drains have altered the hydrology, making these tributaries unstable with high stream velocities causing sediment loading from bed and bank erosion. Annually, about 1,600 tons of sediment erodes from the stream banks in Watts Branch. Essentially 100 percent of Watts Branch has been channelized or altered.
Water quality is poor as stormwater runoff transports sediment, pesticides, heavy metals and other pollutants into the stream. Utility lines and stormwater outfalls block fish passage and aggravate erosion. What little habitat that remains for trust resources like birds, fish and other wildlife is severely degraded. The potential for this stream to recover on its own is poor as there is little evidence of recovery in the past three decades.
Because of the severe impairment, the Service rated Watts Branch as a high restoration priority. To improve wildlife habitat and provide fish passage, the Service will restore streams to natural, stable, self-sustaining conditions. Additionally, to improve water quality, the D.C. Department of Health, Watershed Protection Division will use Best Management Practices throughout the watershed and the Washington Water and Sewer Authority will tackle the problem of faulty sewer lines.
Restoration designs will be complete by summer 2006 for the Upper Watts Branch and restoration will begin fall/winter 2006. Specifically, the Service will use a natural channel design to restore degrading areas by adjusting stream planform, cross-section, and profile such that restored streams can accommodate water flow and sediment supply without creating erosion or deposition within, upstream, or downstream of restored reaches.
One of the more significant stream problems occurring in Watts Branch is the degree of incision. Based on the Watts Branch assessment, the appropriate restoration is to restore the stream at the current base level or higher and create floodplain and floodprone areas. Although the floodplain will be narrower than before pre-disturbance conditions, it will still attenuate flow velocities and bank and bed shear stresses during higher flows. Bed features throughout the restoration will include well-developed pool-riffle or pool/step pool-riffle sequences to dissipate stream energy as the water flows over steps or through the meanders.
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