With each new slab of concrete and stretch of pavement, the sensitive waterways of Anne Arundel County are deluged with more polluted, overheated and fast-moving water.

The flow eats away at streambeds, buries grasses under sediment and kills aquatic life.

The solution is to either halt development or find a way to control the water that used to filter through meadows, woods and wetlands before it hit open water.

Since 1984, when the Maryland Department of Environment first required counties to control stormwater runoff, the most common way counties dealt with the problem is through manmade structures called stormwater management ponds.

The goal of the ponds and other stormwater management practices is to keep the runoff at the same level it was before development.

In the land's natural state, trees, meadows, grasses and crops intercept and absorb rainfall while natural land depressions temporarily hold the excess runoff.

But once cleared and graded, the land immediately begins eroding and can no longer handle the rainfall.

The situation worsens after construction. Rooftops, parking lots, driveways and other imper vious surfaces keep the rain from soaking into the ground, leading to immediate runoff.

The increase in runoff can be too much for the existing natural drainage system to handle. The water rushes downward, digging trenches into stream beds and banks and picking up sediment on the way.

In addition, the "first flush" of rainfall washes away all the accumulated pollutants from parking lots, driveways and sidewalks, and rapidly delivers the pollutants into downstream waters.

Taken together, the speed, sediment and pollution of the water kills aquatic insects, freshwater mussels, fish and aquatic habitat.

"Without managing stormwater, you see incised stream channels, erosion, undercutting. The water hits the streams and they take a beating," said Brian Clevenger, project engineer for MDE's Water Management Agency.

But when the water is directed toward a stable holding facility such as a pond, the waters can slowly filter through sand, which naturally cleans away many of the pollutants.

The state is now moving its focus away from controlling the quantity of water and toward protecting the quality. The result of this shift has been a rewritten State Stormwater Management Manual.

The manual lists 14 standards for stormwater management, including requirements to treat all stormwater to remove 80 percent of the suspended solids and 40 percent of the phosphorus.

It also explains the options for counties to explore what is called "best management practices" in finding the stormwater management programs which best suit their environment.

Options other than stormwater management ponds include the use of man-made wetlands, infiltration practices, filtering systems and openchannel systems.

Finally, the manual offers all parties local governments, concerned residents and developers tools for the design, construction and landscaping for their stormwater management.

For more information or a copy of the Stormwater Management Manual, go to MDE's Web site at www.mde.state.md.us.

Published April 16, 2000
The Capital, Annapolis, Md.
Copyright 2000
The Capital, Annapolis, Md.

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