Surface erosion on a clearcut in the Willamette National Forest

Accelerated surface erosion on steep forested slopes of the PacificNorthwest can cause losses in site productivity and in water quality.Both factors are subject to Federal Laws mandating monitoring.
The study was conducted in the Western Cascades on the Blue RiverRanger District, Willamette National Forest. The timber type wasDouglas Fir. The research had two key objectives:
Development of an effective monitoring system.
Determination of rates of surface erosion after timberharvesting.
Twenty-four catchment boxes with suspended sediment collectors wereinstalled, twenty boxes within a 9 ha clearcut and the remaining four inan adjacent forested area. The measured surface erosion rates weresimilar to those found in previous surface erosion studies in forestedareas.
NO measurable surface erosion occurred at the forest control plots.
Rates of surface erosion in the clearcut increased after burning. Ratesthe second year after burning were the greatest; surface movementdecreased the following year.
Mean values for the pretreatment year 1980 and for 1981 to 1983were 0.03, 0.53, 0.80 and 0.27 T/ha/yr.
Statistically significant differences were difficult to find. Sitevariability and the limited number of plots both contributed to this.Slope was the most significant variable determining erosion rate.
Future monitoring needs should include better climatic data,vegetative recovery data and the spatial distribution of dead and livingorganic material. The factors of slope length, slope shape, organicmaterial protecting the surface and aggregate stability need furtherinvestigation.