Assessing soil degradation by landuse-cover change in Coastal Lebanon

ABSTRACT

Change in landuse is rapid in Lebanon straining its narrow coastal strip. Chaotic urban expansion in the last forty years resulted in consumption of prime soils and degradation of most productive lands. This study aims to show such expansion in Tripoli, the country's second largest city of 61.5 km[2], and to evaluate the impact of landuse change on soil sealing and degradation by integrating remote sensing and GIS techniques. It will gear to more optimal landuse planning based on assessing the result of chaotic landuse change. Social and economic soil functions were involved and soil capability and land suitability compared. Quantifying land cover/use change in the pilot area was arrived at through analysis of multitemporal sources using airborne-based detailed topographic maps [120000 scale] from 1962 and satellite imagery IRS-1C, 5-meter resolution from 2000. The topographic maps contain detailed information on land use, like agriculture and type of forest with corresponding borderlines, urban areas with real geometric shapes and other info. This allowed identifying and grouping the data and comparison with that gathered from the high-resolution satellite images.The resultant change showed an increase of 208% of urban area with a decrease of 35% in agricultural lands. Secondary forest and shrubs replaced the orchards on the abandoned lands. Concerning land capability, 32% of class 1 [prime land] and 26% of class 2 land, i.e. 971 ha, were converted into urban area. Obviously, urban expansion occurred at the expense of rare fertile soils with citrus orchards of the coastal plain like Fluvisols, Luvisols and Cambisols belonging to the most productive agricultural land. Major structural changes in landuse between 1962 and 2000 occurred in the agricultural and urban sectors. Analyzing current landuse pattern, in view of requirements for sustainability, shows that about 10% of prime lands were properly used. Overall, only 22.6% of land is fairly used, while 46% is poorly used and 31.4% is misused. Providing a proper management of water resources, the geographically isolated southeast area with productive lands currently allocated for low-income olive monoculture could be used for more balanced agricultural production. Water harvesting and management will also provide adequate irrigation water for perurban agriculture