United States Forest Service research on sediment production from forest roads and timber harvest areas

Burroughs, E.R., Jr.; Foltz, R.B.; Robichaud, P.R. 1991. United States Forest Service research on sediment production from forest roads and timber harvest areas. In: Actes Proceedings Actes 2: 10th World Forestry Congress; 1991 September 18-22; Paris, France. Rev. For. Francaise 2. Rome, Italy: Food and Agricultural Organization of the United Nations: 187-193.

Keywords: road

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Abstract: The United States Forest Service is developing a surface erosion model for disturbed forest sites, principally forest roads and timber harvest areas. Simulated rainfall is used on bounded plots of various sizes to generate runoff and sediment production from a wide range of soil textures and land management situations. The usual sequence of rainfall at a selected intensity is a 30-minute application with the soil in a dry condition, followed 24-hours later by a second application, then followed as soon as possible by a third. Two rainfall intensities are used on forest roads: 25 mm/hr and 51 mm/hr. Several rainfall intensities are used on timber harvest sites, ranging from 51 mm/hr to 102 mm/hr. Data from simulated rainfall on small field plots, burned and unburned, with and without the residual root mat removed, showed the increases in sediment yield to be expected from severe slash treatment/site preparation burns. Field plots on timber harvest areas that were unburned and burned with and without machine compaction provided data on the effects of these treatments under natural rainfall conditions. Results of a laboratory study of the hydraulic roughness of overland sheet flow with rainfall and a field study of the hydraulics of concentrated flow in wheel ruts were used in an analytic model of runoff from forest roads. Data from a laboratory study of the relative erodibility of wildland soils were used to estimate interrill sediment detachment as a function of soil texture and clay mineralogy. Simulated rainfall on bounded road plots up to 38 m long showed that wheel ruts increased sediment production by a factor of two to four over similar unrutted road sections. The difference in the increase was a function of relative soil erodibility.

Moscow FSL publication no. 1991e