Effects of timber harvesting on the lag time of Caspar Creek watershed

Abstract

Abstract - Hydrograph lag time was analyzed to determine changes after road construction and after selective, tractor-yarded logging in a Caspar Creek watershed, Mendocino County, California. The paired watershed technique was used. Hydrograph lag time for each storm was the time separation between the midpoint of precipitation and the time coordinate of the runoff centroid. No significant change in lag time was detected after road construction. After logging, the lag time generally increased for small, early fall storms and decreased for larger storms. To determine whether the change after logging was influenced primarily by the rising or falling limb of the hydrograph, each hydrograph record was split at the peak and the lag time was measured to the centroid time coordinate of each segment. A statistically significant reduction in both the rising and falling limb lag times was observed. Six hydrologic variables were examined as predictors of the effect of logging on lag time. Proportion of area logged and the ratio of proportion of area logged divided by the storm sequence number were the best predictors. Other variables examined were North Fork peak flow, storm sequence number, storm size, and antecedent precipitation

Citation

Sendek, Karen Hardison. 1985. Effects of timber harvesting on the lag time of Caspar Creek watershed. M.S. Thesis, Humboldt State University, Arcata, California. 46 p.