Chapter 19 - Landslide Hazard Zonation

Abstract

The landslide hazard zonation (LHZ) map is an important tool for designers, field engineers, and geologists to classify the land surface into zones of varying degree of hazards based on the estimated significance of causative factors that influence stability. The LHZ map is a rapid technique for hazard assessment of the land surface it is used for numerous purposes like to help planners and field engineers identify the hazard-prone areas, therefore enabling them to choose favorable locations for site development schemes. If the site cannot be changed and it is hazardous, zonation before construction helps with adopting proper precautionary measures to tackle the hazard problems. There are three categories of scale on LHZ maps: mega–regional: scale of 1:50,000 or more, macro-zonation and risk zonation: 1:25,000 to 1:50,000, and meso–zonation: Scale of 1:2000 to 1:10,000. LHZ was developed by Anbalagan's; many researchers have developed various methods of landslide zonation, but they are not based on causative factors. The main merit of Anbalagan's method is that it considers causative factors in a simple way. The technique, in a broader sense, classifies the area into five zones on the basis of the following six major causative factors: lithology: characteristics of rock and land type, structure: relationship of structural discontinuities with slopes, slope morphometry, relative relief: height of slope, land use and land cover, and groundwater condition.