Great Lake Bulletin Spring 1998

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How Sprawl Threatens Water

Quality
As rain and snowmelt wash acrossrooftops, roads, highways, and parking lots,the water gathers sediments, oils, solvents,and other pollutants before flowing intodrains that lead directly to rivers, streams,and lakes. Run-off from such hard"impervious surfaces" is the largestuncontrolled source of water pollution inthe nation, according to the U.S.Environmental Protection Agency.
As sprawling development surges innorthern Michigan, local governments areresponding to the threat to the region'sclean water by conducting research to betterunderstand how to minimize this runoff.
A starting point is to find out the extentof impervious surfaces in a watershed. InGrand Traverse County, the DrainCommissioner's Office recently completedan analysis of aerial photographs in theMitchell Creek watershed, which drainsinto Grand Traverse Bay.
Ron Harrison, who conducted the study,noted that irreversible harm to water qualityoccurs when more than 10% of the land iscovered with impervious surfaces. Mr.Harrison found that seven of the 29drainage basins in the Mitchell Creekwatershed already have impervious cover ofmore than 10%.
Four years ago, the South CarolinaCoastal Conservation League comparedsprawling and more compact developmentto determine which approach led to greaterlevels of runoff. The study concluded thatcompact development is better for waterquality because there are fewer impervioussurfaces, and more open space remainsavailable to absorb rain and snow.

CONTACTS:
Ron Harrison, Office of the Grand TraverseCounty Drain Commissioner, 616-922-4624; Dana Beach, South Carolina CoastalConservation League, 803-723-8035.

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"Water seeks its own level." Unpaved ground absorbs and filtersrainwater and snowmelt. But as more ground is covered withasphalt, concrete, and sprawling single-story buildings, run-offcontaining sediments, oils, solvents and other pollutants funnelsstraight to rivers, lakes, streams, and bays. At right, the GrandTraverse Mall and Grand Traverse Crossing south of Traverse City.



	How Sprawl Threatens Water
Quality As rain and snowmelt wash acrossrooftops, roads, highways, and parking lots,the water gathers sediments, oils, solvents,and other pollutants before flowing intodrains that lead directly to rivers, streams,and lakes. Run-off from such hard"impervious surfaces" is the largestuncontrolled source of water pollution inthe nation, according to the U.S.Environmental Protection Agency. As sprawling development surges innorthern Michigan, local governments areresponding to the threat to the region'sclean water by conducting research to betterunderstand how to minimize this runoff. A starting point is to find out the extentof impervious surfaces in a watershed. InGrand Traverse County, the DrainCommissioner's Office recently completedan analysis of aerial photographs in theMitchell Creek watershed, which drainsinto Grand Traverse Bay. Ron Harrison, who conducted the study,noted that irreversible harm to water qualityoccurs when more than 10% of the land iscovered with impervious surfaces. Mr.Harrison found that seven of the 29drainage basins in the Mitchell Creekwatershed already have impervious cover ofmore than 10%. Four years ago, the South CarolinaCoastal Conservation League comparedsprawling and more compact developmentto determine which approach led to greaterlevels of runoff. The study concluded thatcompact development is better for waterquality because there are fewer impervioussurfaces, and more open space remainsavailable to absorb rain and snow. CONTACTS: Ron Harrison, Office of the Grand TraverseCounty Drain Commissioner, 616-922-4624; Dana Beach, South Carolina CoastalConservation League, 803-723-8035.


		"Water seeks its own level." Unpaved ground absorbs and filtersrainwater and snowmelt. But as more ground is covered withasphalt, concrete, and sprawling single-story buildings, run-offcontaining sediments, oils, solvents and other pollutants funnelsstraight to rivers, lakes, streams, and bays. At right, the GrandTraverse Mall and Grand Traverse Crossing south of Traverse City.