Development
WHAT DOES DEVELOPMENT DO TO OUR FRESH WATER?
In an undeveloped watershed, most rain and snow falling on the watershed either infiltrates into the ground or is taken up by vegetation. Much of the water that infiltrates into the ground eventually makes it into streams or lakes through groundwater seeps, or springs. Water taken up by vegetation cycles back into the atmosphere through evapotranspiration.
Because of these processes, runoff from natural areas is negligible, except after the largest storms. Ecologically intact systems provide a number of services to the community, including; groundwater recharge, pollutant removal, temperature reduction, erosion control, air purification, flood and drought control, wildlife habitat, increased property values, and recreation.
As development within a watershed increases, it brings with it an increase in impervious surfaces. Water runs directly off these surfaces and into lakes and streams. This causes many problems for the stream and its inhabitants. In highly impervious watersheds, the stream receives a flood of runoff water just after rainfalls or large snowmelts, but is deprived of water during dry times.
Both the high flows and the low flows are problematic for the stream. The high flows can damage aquatic habitats and scour the banks, while low flows deprive aquatic wildlife of water and oxygen. Runoff water is also much warmer than groundwater, and carries with it soil and whatever substances it may pick up from the landscape along the way, such as fertilizer, pesticides, oils, and other pollutants. The system loses its capacity to provide the ecological services mentioned above.
The pollution in the unfiltered runoff is called “nonpoint source pollution” because it does not come from one specific source such as a factory, but rather, it results from our everyday activity on home sites, businesses, roads and farms.
Learn more about the connection between land use and water quality in the HRWC article Speaking Up for Density, and in the HRWC white paper “Watershed Planning: Determining Impervious Surface Capacity to Better Manage Growth at the Rural/Urban Fringe”
The watershed of Fleming Creek, in Superior Township, is mostly undeveloped, with less than 10% of its watershed made up of impervious surfaces.
The watershed of Honey Creek, in Scio Township, has undergone significant suburban development; over 15% of its watershed is made up of impervious surfaces. The creek is receiving large amounts of runoff during rainfalls, as evidenced by the siltation of the creek bottom.
The watershed of Millers Creek, in Ann Arbor, has more than 25% impervious surfaces. When it rains, high flows scour the creek, eroding the banks.
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