Identification of Potential Natural Slope Failure Zones by Geomorphological Analyses Using Raster Slope Shading of LiDAR; Case Study from Kegalle, Sri Lanka

Abstract

There are three approaches to defining the potential instability zonation of natural slopes. The first approach is to understand the failure mechanism through soil properties in a slope, and the mechanisms of failure and movement. The second approach aims to understand the tendency of slopes to fail, with terrain factors that form the essential characteristics of slopes. Understanding the spatial distribution of slope failures and their patterns on a particular slope is the third approach and the focus of this research. All approaches require field verification with expert knowledge. Slope failure zones contain unique topographic patterns that can be used to identify the failure shape and its dimensions. Slope failures are one of many natural denudation processes. Most slope failure landform units, considered as past slope failures tend to expand naturally. If there is no human involvement, zones of past natural slope failure can be also categorized as potential zones of future slope failure. The large-scale geomorphological analysis is the best approach for clearly identifying landform units associated with potential zones of slope failures. The best scale is 1:10,000. Two-dimensional or three-dimensional raster interpretation of slopes can be used to visualize more clearly the actual shape of slope failures. For the study, raster geomorphological mapping uses LiDAR survey data to characterize the landform units of slope failures and to prepare a landslide susceptibility evaluation.