Paper No. J04041 of the Journal of the American Water Resources Association (JAWRA).
Ground-Water Response to Forest Harvest: Implications for Hillslope Stability1
Article first published online: 12 FEB 2007
© 2007 American Water Resources Association. No claim to original U.S. government works
JAWRA Journal of the American Water Resources Association
Volume 43, Issue 1, pages 134–147, February 2007
How to Cite
Johnson, A.C., Edwards, R.T. and Erhardt, R. (2007), Ground-Water Response to Forest Harvest: Implications for Hillslope Stability. JAWRA Journal of the American Water Resources Association, 43: 134–147. doi: 10.1111/j.1752-1688.2007.00011.x
- Issue published online: 12 FEB 2007
- Article first published online: 12 FEB 2007
- Received February 17, 2004; accepted March 16, 2006.
- harvest impact;
- sediment delivery;
- watershed management
Abstract: Timber harvest may contribute to increased landsliding frequency through increased soil saturation or loss of soil strength as roots decay. This study assessed the effects of forest harvest on hillslope hydrology and linked hydrologic change before and after harvest with a simple model of hillslope stability. Observations of peak water table heights in 56 ground-water monitoring wells showed that soil saturation levels on hillslopes differed significantly with harvest intensity at one of the two study locations following 25%, 75%, and 100% harvest. Before the forest was cut 100%, the average rainfall needed for 50% saturation of the soil was 54 mm, but after clearcutting soils reached an equivalent saturation with 61% less rainfall (21 mm). Hillslope stability model results indicate that shallow soils at both study locations, with slopes generally < 30° (58%), were not steep enough to be affected significantly by observed increases in saturation. The stability model indicates that with 100% harvest, there is a 7% reduction in the factor of safety for slope gradients of 35° (70%) with soil depths of 1.25 m. Forest managers may be aided by an understanding that variable hydrologic effects may result from similar forest harvests having different landscape position, land contributing area, and soil depths.