Minor Drainage
An effort has been made to italicize technical words or phrases and clearly define them in the glossary.
Minor drainage has been used as a silvicultural tool in the South since the 1940s on flatwood sites with an excess of surface water for a portion of the year. In recent years some of these sites have been designated jurisdictional wetlands. Activities on jurisdictional wetlands are subject to federal regulations under the Clean Water Act.
The purpose of minor drainage is to remove excess surface water to facilitate access and regeneration. The degree of drainage is determined by ditch depth, ditch spacing, surface topography, and soil characteristics. It is impossible to prescribe specific minimum ditch depth and spacing without evaluating the site. Each drainage system must be designed for a specific site.
Minor drainage for silvicultural purposes does not require a permit because of silvicultural exemptions under Section 404 of the Clean Water Act. However, such drainage must be part of an "ongoing" silvicultural operation. Minor drainage may not be used to convert a jurisdictional wetland to an upland.
The South Carolina Forestry Commission (803-896-8800), U.S. Army Corps of Engineers in Charleston (803-727-4731), U.S. Environmental Protection Agency in Atlanta (404-347-4015), and U.S.D.A. Natural Resources Conservation Service (803-253-3935) are available for consultation and guidance.
BMPs
- Use minor drainage only where it is necessary to minimize harvesting impacts or to facilitate regeneration of desired wetland species.
- The depth, spacing, and number of ditches in a drainage system should only be sufficient to remove excess surface water.
- Design ditches to minimize the need for frequent maintenance.
- Place spoil so as not to impede the entry of surface water into the ditch. Use culverts if necessary to prevent ponding.
- Empty ditches into areas where the runoff will be diffused and filtered by the forest floor before reaching a natural channel.
- Maintain ditches only as frequently as necessary to keep the drainage system functioning. Place fill on either side of a ditch, preferably the uphill side.
Avoid
- Converting jurisdictional wetlands to an upland.
- Emptying a drainage ditch directly into a perennial or intermittent stream.
- Re-dredging ditches deeper than original depth or width.
- Causing ponding of surface water through placement of ditch fill.
- Using silvicultural exemptions to try to achieve non-silvicultural objectives.
NOTE: "Jurisdictional wetland", "minor drainage", and "ongoing silvicultural operation" have not been precisely defined at the time of this publication. Drainage ditch construction, intended for purposes other than minor drainage, requires a permit from the U.S. Army Corps of Engineers (803-727-4731). Violations of the federal regulations governing drainage ditch construction in wetlands can result in stiff penalties including fines and jail sentences.
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Timber Harvesting /
Site Preparation /
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Endangered Species Act /
Additional Management Options: Wildlife Management /
Glossary
Forest Management/ Reference Resources / Environmental Forestry/ Braided Stream Systems