Erosion processes affecting clearcut slopes in the Tenmile Creek Basin, Sequoia National Forest

Thesis (M.S.)--Humboldt State University, 1994Clearcutting is a common timber harvest method in the Sequoia National Forest. Clearcuts are managed to minimize the amount of erosion off of hillslopes, but the timber harvesting practices invariably lead to erosion which would not have occurred if the trees had not all been removed. This research project deals with investigating the erosion processes affecting six clearcuts in the Tenmile Creek Basin of Sequoia National Forest. Erosion processes were identified on the six clearcuts and in neighboring forested areas. Causal relationships between the processes affecting the clearcuts, physical features of the slopes, and the timber harvest methods employed were developed. Rates of sediment mobilization were determined over a one-year period on the clearcuts, and by the use of radiocarbon dating of organic material at the base of the forested slopes.\ud Results of the investigation indicated that several processes, including dry creep, gullying, and organic debris sliding, predominate on the clearcut slopes but are rare or absent in the forested areas. Comparison of sediment mobilization rates on the clearcuts to the sediment deposition rates at the base of the slopes shows that these rates differ by a factor of 2.4 to 5 times the sediment deposition rate