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119 Land Use and Landcover Effects on Runoff Processes: Forest Harvesting and Road Construction

Part 10. Rainfall-Runoff Processes

  1. L A Sampurno Bruijnzeel

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa124

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Sampurno Bruijnzeel, L. A. 2006. Land Use and Landcover Effects on Runoff Processes: Forest Harvesting and Road Construction. Encyclopedia of Hydrological Sciences. 10:119.

Author Information

  1. Vrije Universiteit, Department of Hydrology and Geo-Environmental Sciences, Amsterdam, The Netherlands

Publication History

  1. Published Online: 15 APR 2006

Abstract

The hydrologic impacts of various forestry operations are reviewed, notably the effects of thinning, selective harvesting, clear-cutting with and without roads, and removal of understorey or riparian vegetation. Thinning and selective logging have a relatively modest effect on amounts of rainfall reaching the forest floor unless at least 70% of the standing biomass is removed. The effect on soil water and streamflow is smaller still, mostly because of the increased vigor of the remaining vegetation. Removing understorey vegetation produces a similarly small effect. The annual water yield is invariably increased in proportion to the amount of biomass harvested, with the exception of forests subject to high fog incidence or old-growth forest of low vigor. Cutting riparian vegetation produces a larger increase in streamflow (compared to cuts away from the streams) under subhumid conditions and shallow water tables only. The largest seasonal increases in flow after clear-cutting are normally observed at times when water deficits in the undisturbed forest are highest. The gains in streamflow after clear-cutting gradually disappear when regrowth is allowed, the effect lasting longer where soils are deeper and forest regeneration slower. Mechanized harvesting practices and road building both increase stormflow volumes and peak discharges. The relative effect diminishes with storm size in the case of clear-cutting only, but increases in the case of roads only. Similarly, effects of forest cutting per se on stormflows are “diluted” at larger scales, but the effect of the associated road network is not. Various measures are discussed to minimize the adverse hydrologic impacts of timber harvesting operations.

Keywords:

  • best management practices;
  • clear-felling;
  • forest hydrology;
  • logging roads;
  • riparian zone;
  • selective logging;
  • storm runoff;
  • thinning;
  • watershed management;
  • water yield