Remote Sensing Contribution to the Detection of Karst Features and their structural Environment in the Area of the Bekaa Valley in Central-Lebanon

Abstract

More than two-thirds of the area of Lebanon is covered by lime-and dolostones prone to karst processes, and, thus, developed surface karst features, such as poljes, dolines, uvalas, caves, and blind valleys. This study aims to map the surface karst features, especially sinkholes, and to identify their orientation and dimensions, as well as the tectonic pattern influencing their development based on remote sensing data and references. As karst affected areas are at a higher risk of environmental pollution of the aquifers in the densely populated area due to the karst specific surface and subsurface drainage conditions, the knowledge of the structural pattern and fault systems influencing surface infiltration and groundwater flow is important. This study is focused on the evaluation of optical satellite data (Landsat, Sentinel 2) as well as of radar images (Sentinel 1, ALOS PALSAR) and on Digital Elevation Model (DEM) data (SRTM, ASTER, ALOS PALSAR) and DEM derived morphometric maps aiming to detect traces of karst features, fault zones and their related structures, combined with other geoscientific data of Central-Lebanon. DEM derived maps support the detection of areas with higher surface water input due to their specific local morphometric disposition. The evaluations of the different data sets clearly show that sinkholes and springs in Central-Lebanon are concentrated along a nearly semi-circular belt along western part of the left-lateral Yammouneh shear fault zone. The main factors influencing the occurrence and distribution of surface karst features could be derived by the combined analysis of remote sensing data and reference information.