Forest Service Engineering research to develop a model of onsite sediment production from forest roads and timber harvest areas

Burroughs, E.R., Jr. 1991. Forest Service Engineering research to develop a model of onsite sediment production from forest roads and timber harvest areas. In: Proc. Forestry and Environment - Engineering Solutions, Am. Soc. Agric. Eng., 1991, New Orleans, LA. 151-160.

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Abstract: Forest land management activities in the United States have extended and accelerated in the past four decades into steep, mountainous lands, and into more economically and environmentally marginal operating situations. Also, increasing environmental awareness over the last 25 years has focused considerable attention on the potential impacts of any forest-based activity upon the environment. Of particular concern is soil loss leading to reduction of future forest productive capacity, water quality degradation, damage to aquatic ecosystems, and visual degradation. In many parts of the nation, particularly the Pacific Northwest, forest land managers have found that their management alternatives are constrained by limits on turbidity and sediment concentration allowed in receiving streams. It is essential that managers have the means to predict, with acceptable accuracy, sediment production from alternative road construction and maintenance plans and alternative harvest area treatment practices.

In 1986, the U.S. Department of Agriculture, Agricultural Research Service, initiated the Water Erosion Prediction Project (WEPP) for use on croplands and rangelands to replace the Universal Soil Loss Equation. The Forest Service joined the WEPP effort because of our interest in estimating sediment production from disturbed forest lands. The WEPP model cannot be used in its present form on forest sites because of the many hydrologic and erosion conditions that are not considered in the cropland WEPP model. The goal of our work is to develop physical process models of onsite runoff and sediment production for use on forest roads and timber harvest areas nationwide. To do this, we must develop algorithms to estimate model parameters using easily measured site characteristics from field sites across the nation. This "forest model" will become an integral part of the general WEPP model.

Observations and experience by forest land managers and technical specialists nationwide indicate that forest roads are the greatest single source of sediment delivered to receiving streams. Probably the greatest volume of sediment produced from Alaska to California and the northern and central Rocky Mountains comes from mass erosion associated with forest road construction and maintenance. A lesser volume comes from surface erosion on the forest road prism, and a much smaller volume from landslides and surface erosion on timber harvest areas. Fall and winter rains, and spring snowmelt runoff in the west, provide ample energy for surface erosion.

Moscow FSL publication no. 1991f