Science et changements planétaires / Sécheresse


Caractérisation morpho‐pédologique des zones karstiques du Liban Sensibilité des sols à l‘érosion hydrique Volume 14, issue 4, OCTOBRE-NOVEMBRE-DÉCEMBRE 2003


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Conseil national de la recherche scientifique\Centre national de télédétection, BP 11‐8281, Beyrouth, Liban. <rsensingcnrs.edu.lb> Institut national agronomique Paris‐Grignon, BP 1, 78850 Grignon, France. <michel‐claude.girardgrignon.inra.fr>

In Lebanon, the sensitivity of different landforms to water erosion is not yet clearly identified, notably when understanding the water flow regime is not sufficient. This is the case of the karstic terrain, which occupies a big region in Lebanon (65% of its area). These terrains are distributed in localities having various lithologic and soil properties and they are characterized by different responses to carbonate dissolution. In this study, a full typology of the Lebanese karstic terrain is developed. Four karstic zones have been identified: the dolines zone; the lapies zone; the covered karst zone; and the open karst zone. They vary in topographic form, in dissolution response due to the impact of the climate, and in geographic location altitudes over 2,000; between 1,000 and 1,500 m; between 500 and 1,500 m; and between 500 and 2,000 m. The field observations reveal that different soil properties characterize these zones as well as various water flow regimes. The statistical interpretation of field data indicates that the karstic terrain can be considered as having a relatively low level of water erosion. In fact, the median volumes of soil losses are equal to 0.91, 0.08, 2.89 and 0.02 tons\ha\year in the doline zone, lapies zone, covered karstic zone and open karstic zone, respectively.