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Surface Water - Threats
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The following information was adapted from "Watershed Resource Papers" developed for the Dowagiac River Watershed Project by Langworthy, Strader, LeBlanc, & Associates, Inc.
Surface water features - lakes, streams, rivers, and ponds - are directly affected by land development. Soil erosion, impermeable surfaces (such as parking lots and roofs), soil contamination, and recreational activities can each affect surface water quality
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Threats: Non-point Source Pollution
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Non-point source pollution poses one of the greatest threats to surface water. Rather than occurring from one major source, like a sewage treatment plant or industrial use, non-point source pollution results from rainfall or snowmelt moving over and through the ground. As this runoff moves, it picks up and carries away natural and human-made pollutants. These are deposited into lakes, rivers, wetlands, ponds, and groundwater.
In the rural areas of Michigan, including the Dowagiac River Watershed, sources of non-point contamination include a combination of agricultural practices, lawn chemicals, soil erosion, and stormwater runoff. Of these, control of impervious surfaces (such as roofs and roads), from which stormwater runoff flows is an area where local governments may have a significant influence.
Impervious surfaces may cover anywhere from five to ten percent or more of a site. Smaller sites may have significantly higher coverages, particularly those with commercial and industrial uses with large parking areas. Not only quantity, but quality of runoff from normal precipitation may change considerably, as lawns, roads, and parking lots rinse clean. Other unnatural water sources are added, such as construction cleanup, car washing, or lawn watering.
Traditionally, channelization, dams, and storm sewers have been used to control the effects of runoff from development and increased impervious surfaces. While these measures may reduce flooding potential by diverting water, they do not address water quality.
For more information about Non-point Source Pollution, click here.
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Threats: Impervious Surfaces
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Impervious surfaces may cover anywhere from five to ten percent or more of a site. Smaller sites may have significantly higher coverages, particularly those with commercial and industrial uses with large parking areas. Not only quantity, but quality of runoff from normal precipitation may change considerably, as lawns, roads, and parking lots rinse clean. Other unnatural water sources are added, such as construction cleanup, car washing, or lawn watering.
Traditionally, channelization, dams, and storm sewers have been used to control the effects of runoff from development and increased impervious surfaces. While these measures may reduce flooding potential by diverting water, they do not address water quality.
For more information about Impervious Surfaces, click here.
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Threats: Stormwater, Soil Erosion & Sedimentation
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Ideally, stormwater can be managed in a fashion which will not substantially alter the natural hydrologic regime, especially as it relates to the quantity of runoff (from rainfall) versus infiltration within a watershed. As more development takes place, either on large projects or on small home sites, the disturbed land loses its ability to hold soil in place. Natural vegetative cover is replaced by roof tops, roadways, parking lots, and other impervious surfaces. The increase in impervious area will greatly increase the rate and volume of runoff and decrease water infiltration into the ground.
As a result of these newly developed impervious areas, rainfall can easily overcome the ability of soil to remain in place. As rainfall hits the disturbed soil it has two choices; if on flat ground some may percolate into the groundwater; the remainder will either pond on the site, or find the most direct route available to run off the site, taking soil and pollutants along with it in the form of stormwater.
With sediment being the largest pollutant by volume entering the watershed's streams and lakes, erosion and sediment control is of the utmost importance. Erosion and sedimentation results in loss of fertile topsoil, filling of lakes and streams, increased flooding, damage to aquatic habitat and animals and structural damage to buildings and roads.
The purpose of Part 91, Soil Erosion and Sedimentation Control, of the Natural Resources and Environmental Protection Act (P.A. 451 of 1994, as amended) is to control soil erosion and to protect the waters of the state from sedimentation. This law requires that a permit be obtained for all earth changing activities that disturb one or more acres of land or is within 500 feet of a lake or stream. To obtain the permit, a soil erosion and sedimentation control plan must be submitted that effectively reduces soil erosion and sedimentation and identifies factors that may contribute to soil erosion and sedimentation.
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