Wednesday, May 20, 2009

Storm Water Challenges in Silver Spring

This week, I explored the dramatic erosion to the hillsides bordering the Paint Branch stream valley caused by uncontrolled storm water. My guide was Diane Cameron, Conservation Program Director of Audubon Naturalist Society, who has been working on storm water and environmental protection issues in Montgomery County for many years.




The Grand Canyon of Paint Branch is the result of uncontrolled storm water running off the roofs and parking lots of a corporate office park, east of Route 29, in Silver spring, MD. The enormous volumes of water have eroded tons of soil and rock and have carved a "canyon" into the hillside.


The storm water runs into one of Montgomery County's most pristine streams, the Paint Branch, a tributary of the Anacostia River.





According to the Maryland Department of the Environment, “urban development has a profound influence on the quality of Maryland’s waters. To start, development dramatically alters the local hydrologic cycle. The hydrology of a site changes during the initial clearing and grading that occur during construction. Trees, meadow grasses, and agricultural crops that intercept and absorb rainfall are removed and natural depressions that temporarily pond water are graded to a uniform slope. Cleared and graded sites erode, are often severely compacted, and can no longer prevent rainfall from being rapidly converted into stormwater runoff.”

“The situation worsens after construction. Roof tops, roads, parking lots, driveways and other impervious surfaces no longer allow rainfall to soak into the ground. Consequently, most rainfall is converted directly to runoff. The increase in stormwater can be too much for the existing natural drainage system to handle. As a result, the natural drainage system is often altered to rapidly collect runoff and quickly convey it away (using curb and gutter, enclosed storm sewers, and lined channels). The stormwater runoff is subsequently discharged to downstream waters such as streams, reservoirs, lakes or estuaries.”

“Water Quality is affected by the accumulation of trash, oil and rubber from cars, fertilizers and pesticides applied to lawns, sediment from bare or poorly vegetated ground and other pollutants entering streams, rivers and the Chesapeake Bay. Inflow of sediment can cloud water, blocking sunlight from submerged plants. Sediment also settles to the bottom of streams, clogging the gravel beds used by fish for laying their eggs. Nutrients, such as phosphorus and nitrogen, from fertilizers enter the water and promote unusually rapid algae growth. As this algae dies, its decomposition reduces or eliminates oxygen needed by fish, shellfish, and other aquatic life for survival.“

As the following map from the County's Department of Environmental Protection shows, the water quality in the Silver Spring area is "poor."


For more information, visit http://www.mde.state.md.us/Programs/WaterPrograms/SedimentandStormwater/home/index.asp

To learn what you can do about storm water and improving the quality of the water in the creeks and streams, check out these websites. There are several important organizations that are concerned with storm water and stream restoration: Friends of Sligo Creek, the Audubon Naturalist Society, and Stormwater Partners.

2 comments:

Chris Victoria said...

The good news is that this type of instability is very correctable, with the right approach. The wrong approach would be for the County to fill it with riprap and create a uniform channel all the way down to the confluence with Paint Branch. A steep, cascading channel--like you'd find in the mountains--with properly spaced pools needs to be created here to step the water down to Paint Branch without excessive erosion (a Rosgen B2 or A2 type system).

Additionally, some assessment of the stormwater issues causing the problem should occur, so that chemistry improvement can also be made through the installation of some type of BMP suite. Given the cold water fishery present in this basin, no open water/standing water facilities (wet ponds) should be installed here.

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