Sediment Delivery Ratios and Areas of Forest Operational Features by Physiographic Groupings in the Southeastern U.S.

Forests of the Southeastern United States produce approximately 12% of all the world's wood products and represent 40% of all U.S. timberland, thus emphasizing the importance of Southeast in support of the United States' role as the world's largest timber producer. Producing such quantities of timber requires a substantial areas of forest harvest operations, which have the potential to disturb soils, facilitate erosion and potentially reduce water quality. Harvest sites routinely contain operational features such as skid trails, harvest areas, haul roads, decks/landings and stream crossings, all of which have the potential to influence erosion and sediment deposition in streams. Forestry best management practices (BMPs) were created to minimize the effects of harvesting operations on sedimentation and are implemented at varying levels throughout the Southeastern U.S.

We quantified the area of these features on 111 recent harvest sites throughout 11 Southeastern states and three physiographic groupings (Mountains, Piedmont, Coastal Plain). No significant differences were found between the groupings with regard to the percent of area occupied by each operational feature. Decks, haul roads, skid trails, and stream crossings comprised an average of 1.43%, 3.21%, 7.03%, and 0.19% of the harvest operations. Roads, decks, skid trails, and structures were combined into an access feature category. These combined access features occupied 13.0% of harvests in the Mountains, 10.2% in the Piedmont, and 10.4% in the Coastal Plain (10.4%). A companion study was developed to trap sediment delivered to the stream and quantify the sediment delivery ratios (SDRs) on a subset of harvests sites in order to determine the average amount of eroded material that could reach a stream from each specific operational feature following a harvest. Across all groupings, stream crossings had the highest average SDR (34.32%), while skid trails had the second highest SDR (21.04%). Substantial site variability resulted in large SDR differences with few meaningful significant differences, but stream crossings, skid trails, and haul roads had sufficiently high sediment delivery ratios across all groupings to warrant additional BMP focus on these areas.