Application of Fuzzy Algorithm for Assessing Seismically Induced Landslide Hazard for an Important Road Corridor in the Lower Indian Himalayas

Abstract

<p>A critical part of planning and managing road infrastructures in mountainous regions is the<br />pragmatic assessment of the prevailing and credible landslides hazard. Such assessments assume<br />greater significance for the Himalayan region, where seismically induced landslides present a<br />greater threat than commonly recognized, and require a robust comprehension of two hazards:<br />earthquake and the landslides induced by the former. However, the traditional practice of<br />landslide hazard assessment often neglects seismic factor due to paucity of pertinent data, which<br />may further be ascribed to the rarity of an extreme event. In this context, an endeavor has been<br />made in this study to evaluate the seismically induced landslide hazard for a scenario earthquake<br />of 10% exceedance probability in 50 years for an important road corridor in the lower Indian<br />Himalayas using Fuzzy algorithms. Probabilistic Seismic Hazard Assessment (PSHA) has been<br />carried out for the study area to calculate the Peak Ground Acceleration (PGA) of the scenario<br />earthquake, which is then used as a landslide triggering factor. PGA is integrated with eight<br />different landslide controlling factors viz. lithology, slope angle, aspect, elevation profile,<br />distance form fault, distance from drainage, distance from road, and land-use-land-cover patterns<br />in a Geographical Information System (GIS). 232 numbers of landslides are mapped for the<br />study area using high resolution Google earth imagery platform. The Fuzzy Cosine Amplitude<br />method is used to define the degree of similarity (strength of correlation) between the observed<br />landslides (dependent variable) and the landslide causative factors (independent variable(s)).<br />Expectedly, the probability of landslide occurrence correlates (degree of similarity) to the PGA<br />in a linear pattern (goodness of fit = 0.9954). The result of the study is discussed in terms of a<br />seismically induced Landslide Hazard Zonation (LHZ) map for the study, which is generated<br />using three Fuzzy operators (AND, OR and GAMMA). The prepared LHZ map demarcates more<br />than 40% of the study area as the zones of high to very high landslide hazard under the scenario<br />earthquake, with a prediction accuracy of 80%. The study shows that probabilistically generated<br />PGA can be included as seismic parameter for a more comprehensive assessment of the landslide<br />hazard in seismically active regions.</p> <p>Keywords: Fuzzy Cosine Amplitude, Probabilistic Seismic Hazard Assessment (PSHA), Peak<br />Ground Acceleration (PGA), Landslide Hazard Zonation (LHZ), the Himalayas</p>