Geotechnical Zoning for Urban Planning in Developing Countries (Duhok Governatorate, Iraq)

Abstract

The goal of this work was to characterize geological zones and assess their associated slope stability, with a focus on landslide susceptibility in developing countries. Geological risk assessment and mapping often require data that are not easily available in these contexts. Assessment was carried out in four key areas located in the northeastern part of Iraq (Duhok Governorate) along the Zagros Fold-thrust belt, encompassing the towns of Bamerne, Zawita, Ba’adrie and Al-Shikhan going from north to south. From a geomorphologic point of view, all the villages are located on the flanks of steep anticlines where slope deposits and large alluvial fans cover the foot slope. Field surveys, improved with remote sensing imagery analysis, and Digital Elevation Model comparison are the methods integrated in the study. Once the geological setting as well as geomorphological features and processes are mapped, a susceptibility zonation of the territory is performed. The classification divides the areas in five susceptibility categories from low (zone 5) to very high (zone 2 and 1). Quaternary deposits (alluvial fan, slope and eluvial-colluvial deposits), are grouped in zone 5 if the slope angle is smaller than 20% and in zone 4 (moderate) for values larger than 20%. In these categories only the geomechanical properties of the terrains are taken into account for the potential susceptibility involving civil constructions and infrastructures. Zone 3 (high susceptibility) is subjected to slope washing phenomena as gully erosion. The last two zones (2 and 1) are characterized by a very high susceptibility degree. Differences in the kinematic of landslide phenomena are observed, with rock falls in zone 2 and slides and debris flows in zone 1. For each study area three maps are produced: a geological, a geomorphological and a susceptibility map, all using a scale of 1:10,000. All five susceptibility categories are present. The results of this study are at the basis of the master plans designed by the local government in order to better inform the development strategies for the cities. This approach may be a promising methodology for urban planning in developing countries since it only takes into account terrain attributes (slope) and the nature of the substrate (dividing the geological nature of the terrain only in bedrock and deposits).