Larson, Keith R. 1981. An evaluation of a procedure for predicting sediment yield increases from silvicultural activities. Corvallis, OR: Oregon State University. 81 p. M.S. thesis.
Sediment yield increases following timber harvest and road con-struction were predicted for four Pacific Northwest experimentalwatersheds. Sediment yields were predicted using a handbook developedby the U.S. Forest Service entitled, "An Approach to Water ResourcesEvaluation of Non-Point Silvicultural Sources" (WRENS). Predictedsediment yield increases varied from 40 to 180 percent of measuredincreases.
Several conceptual problems and difficulties in the applicationof the procedure responsible for observed differences between pre-dicted and measured sediment yield increases were identified. Majorproblems included (1) sediment budgeting inaccuracies, and (2) no con-sideration of delays in the export of predicted sediment inputs tostream channels due to in-channel sediment storage.
The accuracy and applicability of the WRENS procedure for esti-mating actual sediment yield changes in forest management planning islimited by (1) the unknown and complex nature of several erosion andsediment transport processes, and (2) temporal variability and theprobabilistic nature of rainstorms of extreme magnitude and theireffect on erosion and sediment transport processes.