South County Sector Plan: The Sector Inventory

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Environmental Constraints
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Environmental Constraints
Like much of Knox County, steep slopes, waterways, Karst soils, and sinkholes limit land use development in the South County Sector. The limited availability of sewer and water service results in extensive use of septic fields and wells. Soil type and underlying strata further limit development where poor soils or rocky outcrops demand the use of large tracts of land in order to develop septic fields. Uncontrolled runoff from excavation is the predominant environmental impact resulting from land development. Storm water runoff is increased as a result of increases in nonporous services such as pavements and rooftops. This situation is further exacerbated by the oversteepening of slopes, the operation of borrow pits (soil mining), and a lack of vegetation on graded areas.

Slopes

	Total Acreage	% of Total	MPC Recommended Density
Slopes 0 – 15% slope	25,035.51	60.01%	No additional limitations
Slopes 15 - 25% slope	9,895.41	23.72%	1-3 dwelling unit per acre
Slopes 25 – 40%	5,631.10	13.50%	1 dwelling unit per 2 acres
Slopes > 40% slope	1,157.78	2.78%	No development recommended

Source: MPC, November 2000.
MPC Recommended Density Source: Streambank Development and Water Quality Protection Guidelines, MPC, August 1997.

In order to reduce storm water runoff and erosion, MPC has developed guidelines for building on slopes. The guidelines provide for a reduction in density on slopes over 15%, with increasing density limitations as the slope increases to 40%. MPC does not support development on slopes over 40%.

Development in the South County Sector is severely constrained by steep slopes, waterways, and soil types.

Building on steep slopes increases soil erosion, leading to sedimentation of the waterways.

Development in and around wetlands and waterways can damage critical ecosystems and lead to erosion and sedimentation.

Soils having a high clay content do not adequately filter effluent.

Areas of Karst geology are especially poor locations for development due to the porous nature of the subsurface geology. Toxins and effluent placed into Karst formations can lead to ground water pollution. Construction in and around Karst formations can lead to subsidence and flooding.