Wednesday, April 2, 2003

Planning minimizes problems

Stream crossings on woodland roads are a high priority interest to the landowner or manager of forestlands. Although stream crossings should be avoided, if possible, they are often necessary for timber harvest and access to certain forest sites. Sometimes controversial, stream crossings are also the most critical aspect of forest road systems - when it is necessary to use them. The basic concern is what can happen to a stream crossing, due to improper planning and construction, with regard to erosion and negative effects on water quality.

Pre-planning should involve road-type and road-use patterns, stream (channel) characteristics, and identification of aquatic organisms in the stream. Both permanent and temporary stream crossings should be based on expected storm flow, return intervals and watershed acreage above crossings.

Accurate evaluation of a stream crossing area is vital to success of crossing projects. Watershed size is the first phases of information that must be determined. Topographic maps can be used to locate where roads should cross streams. Drain areas should also be identified and types of ground cover can be evaluated for calculating design discharge for the stream crossing. Regional rainfall data is important in determining the amount of water flow a stream crossing should be designed to channel.

The three most common stream crossings for forest management operations are culverts, bridges, and fords. Culverts are the most common type of stream crossing and can be temporary or permanent. Fords of various types are usually more expensive than culverts and can be used for haul-roads only where the streambed is firm, banks are low and stable, and stream depth shallow. Bridges are the most expensive type of stream crossing, either temporary or permanent, they cause the least disruption to stream flow and have less influence on fisheries than other crossings.

The Georgia Forestry Commission publication "Georgia's Best Management Practices For Forestry" details general and specific BMPs related to stream crossings. Included are recommendations for approaches to all permanent or temporary stream crossings and erosion control structures. A copy of this publication can be obtained from your local GFC office at 770-227-5522 or 770-358-1459. An electronic copy of this publication is available at www.gfc.state.ga.us/Publications/Rural Forestry GeorgiaForestryBMPManual.pdf. More specific information and technical assistance can be obtained from your local Natural Resources Conservation Office (770-957-5705).

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