Science et changements planétaires / Sécheresse


Impact of human activities on water-induced soil erosion in the mountainous coastal region of Lebanon Volume 12, issue 3, Septembre 2001


See all figures

Centre national de télédétection/Conseil national de la recherche scientifique, BP 11-8281, Beyrouth, Liban.
  • Page(s) : 157-66
  • Published in: 2001

Soil erosion by water is a major cause of landscape degradation in semi-humid to semi-arid Mediterranean environments. A typical example of this trend concerns the mountainous coastal region of Lebanon. Humans influence this physical process by activating or reducing it. The most common harmful human activities are mainly excavation for quarrying, construction of buildings and roads, settlement expansion and deforestation (fire and wood cutting). Protective activities are limited to retaining walls, man-made channels and terraces built to provide protection against natural hazards or to conserve land for agriculture. Soil erosion criteria were investigated in an area of high human activity: earth pillars, gullies of all sizes and drifting landmasses. Statistical analysis of the field data indicated that soil excavation (quarries in soft formations) is the human activity that most increases soil susceptibility to water erosion (rainfall or runoff), with a median soil loss volume due to water erosion of 22 t/ha/year on the 25 visited sites. Urban settlement expansion was generally found to have a less destructive effect with respect to soil water erosion (soil loss of 6 t/ha/year). Deforestation had a negligible effect on this process (soil loss of 2 t/ha/year) in comparison to the human activities described above. Retaining walls and terraces usually seemed to provide relatively inefficient protection, except in certain areas where they decreased the negative effect of erosion.