Friday, May 30, 2008

Soil Erosion Model for Lebanon

Erosion hazard is a major land degradation problem in Mediterranean environments. Consequently, many models have been developed for quantifying soil loss or pinpointing areas suffering from soil erosion.

Although increased use of GIS led to a great many GIS-based model applications at the catchment level and larger scales during the past decades, there has been no emphasis on predicting erosion hazard for specific environments such as the peculiar and attractive karst landscapes commonly distributed in the Mediterranean region.

In Lebanon, this landscape makes up 70 percent of the country’s total area. This environment contains particularly fragile ecosystems because thin soils that have low fertility and readily succumb to desertification predominate. In addition, poor land management practices increase soil erosion and the detrimental effects of human activities, such as deforestation, burning, and overgrazing in karst areas, leave only barren soils that are vulnerable to the effects of intense rainfall. Figure 1 shows the study area for the KARSTERO model - a 1,062-square-kilometer area located in the East Mountains.

The goal of this project is conceptualizing - in a GIS framework - a regional, quantitative, and empirical model that would predict erosion in dynamic karst landscapes at a scale of approximately 1:100,000 meters. The study area for developing this methodology is a 1,062-square-kilometer area located in the East Mountains. These mountains, with peaks reaching 2,698 meters, contain numerous types of karst formations such as lapie, sinkholes, and exposed karst. Soil loss studies predict erosion rates reaching as high as 70 tons per hectare. In addition to many seasonally developed channelling systems, three permanent streams - El-Jawz, Ibrahim, and El-Kalb - are carving up the study area. Four microclimatic zones exist and range from the coastal sub-humid to the mountainous oromediterranean. Between 75 and 80 percent of annual rainfall is concentrated between November and April. Intense rain showers of more than 100 mm in 24 hours are common.

Read the complete study here.


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