Assessment of abandoned quarries for revegetation and water harvesting in Lebanon, East Mediterraean

Negative impacts of abandoned quarries in Lebanon include degraded scenery, landscape fragmentation, loss of biodiversity and decreased quantity and quality of water resources. Between 1996 and 2005 the number of quarries increased from 711 to 1278 and the quarried land area increased from 2875 to 5283 ha. Recent remote sensing data (2005) showed that 21.5% were distributed on forested land and arable land while 32.4% of quarries were detected on scrubland and grassland and 3.2% of quarries were distributed inside urban zones. Due to institutional weakness and the absence of national policy, most Lebanese quarries have not been developed using environmental concepts and in preparation for post operation reclamation or restoration. Limited national resources available for reclamation must be targeted toward those quarries where the likelihood of successful reclamation, and thus the likelihood for mitigation of negative environmental impacts, is the greatest. To facilitate such decision making we developed a GIS based model that utilizes geomorphological and pedoclimatic characteristics of the site, including precipitation, slope gradient, slope aspect, rock infiltration, catchment area, the availability of soil material and soil texture to assess probability of reclamation success. Each abandoned quarry was categorized into specific classes with respect to surrounding native vegetation, rainfall and slope gradient. Deserted quarries were assessed for suitability for vegetation establishment and/or water harvesting. Potential revegetation success is strongly linked to slope aspect where southern facing slopes especially in semi-arid areas with annual rainfall below 600mm, were given lower prospects of success in relation to spontaneous revegetation processes. The quantity and quality of soil material adjacent to quarries was included in the vegetation model to evaluate the possibility of providing sufficient mineral substrate from neighboring areas with deep soils possessing good physico-chemical properties for plant establishment and survival. All attributes in the vegetation recovery model were assigned a weighted numeric score which were summed to provide a relative ranking of all quarries. These were then separated into four classes of likely revegetation success. In addition, water harvesting potential was assessed based on catchment area above the quarry and rock permeability in the quarry. The priority for reclamation was based on the comparison of vegetation success and suitability for water harvesting. The results of this model can be used to facilitate decision making concerning priority selection of sites for reclamation efforts, reclamation strategies to be attempted and possible alternative post-reclamation land use.