Geohazards assessment of the karstified limestone cliffs for safe urban constructions, Sohag, West Nile Valley, Egypt

Karstified rock formations are, sometimes, responsible for major hazards to urban development and to human life as well. The cartographic and descriptive inventory of karst phenomenon is a concrete contribution to the management and conservation of those areas where soluble carbonates and evaporites are present at the surface and/or in the subsurface. The present geohazards and risk assessment study concerns with the highly karstified and risky area of Sohag, west of the Nile Valley, Egypt. It is dominated by the top surface of the highly weathered and karstified Miocene Drunka Formation. This highly karstified bedrock was explored and monitored for the presence of caves and sinkholes using the ground penetrating radar 'GPR' and the electrical resistivity tomography 'ERT'. The study succeeded to monitor the less hazardous areas by introducing a hazard assessment map to help in future planning for development. Finally, a panorama for the best engineering treatments is proposed in order to mitigate the hazard related to collapses linked to the presence of some paleodolines. The present study indicated that only the areas that are located to the west and southwest of the study area, close to the mountainous areas and away from the Nile valley, are suitable for constructions.