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Volume 4, Number 4
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How to Slow the Flow

By Jack Greer


For More Information

University of Maryland Department of Engineering (Bioretention) www.ence.umd.edu/~apdavis/Bioret.htm

Maryland Water Resources Research Center www.waterresources.umd.edu/

University of Maryland Extension www.agnr.umd.edu/MCE/Category.cfm?ID=10

Maryland Environmental Finance Center www.efc.umd.edu

National Center for Smart Growth Research and Education www.smartgrowth.umd.edu

Center for Watershed Protection www.cwp.org

Chesapeake Bay Foundation www.cbf.org

Chesapeake Bay Program www.chesapeakebay.net/stormwater.htm

Low Impact Development Center www.lowimpactdevelopment.org

Maryland Department of Natural Resources www.dnr.state.md.us/streams/

U.S. Environmental Protection Agency www.epa.gov/owow/nps/urbanmm/

Maryland Department of the Environment www.mde.state.md.us

Slowing the flow of stormwater is everybody's business. On the front line are contractors and the developers and property owners who retain them. The best time to install stormwater devices is during construction. It's easier and costs a lot less.

Homeowners and businesses must also help to slow the flow. Here are some suggestions:

Rain barrels. Placed at the base of downspouts, they catch runoff from the roof and disperse it slowly, e.g., through a soak hose.

Green roofs. Using carefully designed substrate and plantings, these roof gardens absorb water and provide shade and other benefits.

Infiltration terraces. Rather than forcing water to flow away, these terraces let water seep into the ground.

Permeable pavers and pavements. Unlike conventional asphalt or concrete, these permeable surfaces let water percolate through, reducing runoff.

Grassy swales. Used instead of concrete culverts, these depressions allow water to infiltrate, helping to capture nutrients as well.

Rain gardens (bioretention areas). A form of “vegetated soil media," rain gardens capture runoff and use infiltration and evaporation to slowly disperse moisture, while taking up nutrients.

Sunken medians. Unlike raised medians that drive water away, these depressions gather water and may function like grassy swales or rain gardens.

Barriers That Remain

According to stormwater expert Allen Davis, a number of barriers stymie efforts to reduce runoff.

Lack of understanding. Many local government officials, contractors, or financial officers in charge of letting out bids still do not understand the nature, purpose, or standards for bioretention devices and other progressive stormwater practices.

Lack of information. Good data on how specific stormwater devices perform over time in varying areas are still lacking.

Expense. Stormwater fixes often carry a big cost, especially when old systems must be “retrofit" with newer, more environmentally friendly devices.

Regulatory hurdles. Though Maryland is known for its comprehensive stormwater manual, regulations can still sometimes hinder rather than help.

Inexperience. Contractors and others on the ground often lack experience with new techniques, and may stick with what they know.

Inertia. All these taken together, along with human nature, can lead to a ponderous inertia, with the result that little may change without some countervailing force.

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