Changes in soil moisture and pore pressure after harvesting a forested hillslope in northern California

Abstract

Abstract - In 1987, a 0.83-ha zero-order swale was instrumented with 58 pierometers and 25 tensiometers along several hillslope transects. Through 1993, soil moisture conditions were measured by pressure transducers connected to a digital data logger recording at 15-minute intervals. In August 1989, the 100-year-old second-growth forest in the swale was felled. Logs were removed by cable yarding and heavy logging equipment was excluded from the hillslopes. Increases in peak piezometric levels and soil moisture were observed following logging. In the shallower, unsaturated portion of the soil profile, the increase was short-lived due to the rapid resprouting of redwood stumps. At the soil-bedrock interface, increased pore pressures persisted during winter periods throughout the 4-yr post-harvest period. In addition to changes in evapotranspiration, pore pressure increases may be explained by reduced canopy interception, compaction, or the collapse of soil pipes. At the base of the swale, pipeflow accounted for virtually all of the stormflow. After logging, soil pipes continued to efficiently route surplus stormflows through an existing piping network and no slope instabilities were observed.

Citation

Keppeler, Elizabeth T.; Ziemer, Robert R.; Cafferata, Peter H. 1994. Changes in soil moisture and pore pressure after harvesting a forested hillslope in northern California. In: Marston, Richard A., and Victor R. Hasfurther (eds). Proceedings, Annual Summer Symposium of the American Water Resources Association: Effects of Human-Induced Changes on Hydrologic Systems, 26-29 June 1994, Jackson Hole, Wyoming. American Water Resources Association, Bethesda, Maryland. p. 205-214.