Environmental Engineering Reference
In-Depth Information
relatively flat, with slope gradients less than 8%. From a morphostructural point
of view, Lebanon consists of three units, two of them constituting the uplifted steep
mountain ranges (Mount Lebanon and Anti-Lebanon), separated by the Bekaa de-
pression. The western chain (Mount Lebanon) borders the Mediterranean Sea, dis-
playing relatively gentle slopes on its western flanks and steeper ones on the eastern
side. The highest point in Lebanon is in the northern part of this mountain chain,
namely the Qornet es Saouda, 3083 m above sea level (asl). Precipitation (rain and
snow) falls in abundance on the Lebanese mountain chains, especially on Mount
Lebanon. The precipitation rate varies between 700 and 1200 mm/year with increas-
ing elevations across Mount Lebanon; about 80% of the annual precipitation falls
between November and February (Edgell, 1997).
Carbonate rocks (limestone and dolostone) dominate the known Lebanese rock
succession. The oldest exposed rocks are of Liassic age (Dubertret, 1975). The
Jurassic strata constitute the cores of the Mount Lebanon and Anti-Lebanon ranges.
Cretaceous strata - especially the Cenomanian-Turonian Sannine and Maameltain
formations - form the flanks of the mountain chains, covering most of the country's
surface area. The stratigraphy of Lebanon has been investigated by a number of
authors (Dubertret, 1955; Saint-Marc, 1974, 1980; Beydoun, 1988; Walley, 1997;
Nader, 2000).
The Late Jurassic is characterized by a period of regional uplift, emergence and
erosion. Upon emergence, the Jurassic rock mass was deeply fractured and karsti-
fied before volcanism took place. Subsequently, volcanic deposits and continental
debris filled up the pre-existing fractures and depressions accentuating the palaeoto-
pography (Renouard, 1955; Nader
et al.,
2003).
The morphology of Mount Lebanon has been mainly affected by karstification,
part of the meteoric diagenesis process, since the Miocene (Dubertret, 1975; Walley,
2001).
The Lebanese mountain range is one of the highest in the Mediterranean region,
peaking at more than 3000 m, and the steepness of its slopes, combined with the
rainfall it receives (up to 1500 mm/year), make these mountain lands an excep-
tional agro-ecosystem. The orography creates a mild climate, which differs from
neighbouring arid and semiarid countries. Hence derive the pedoclimatic features
of Lebanese soils. The soil temperature regime is mainly hyperthermic and the soil
moisture regime, because of the typical Mediterranean seasonal rainfall distribution,
is considered to be generally xeric. In the Mount Lebanon range the large areas of
very shallow soils and rocky outcrops lead to episodes of severe erosion and land
degradation. Recent studies have demonstrated that more than 50% of Lebanese
territory is prone to desertification.
Considering the geological, morphological and climatic features of Lebanon, the
country's pedological panorama can be synthetically described as follows. Soils
classified as Petric Calcisols are mostly present in the northeastern Bekaa. Eutric
Fluvisols, Vertic Cambisols and Vertisols appear especially in the central Bekaa.
Eutric Luvisols, Rendzic Leptosols and Lithic Leptosols are the most widespread
soils in the Lebanese mountains. Calcaric Cambisols, Eutric Vertisols, Calcaric
Arenosols and Eutric Fluvisols characterize the soils of the coastal plain.
