Abstract
Problem statement: The study area is frequently subjected to landslides especially alongside the E-W high way. This study demonstrates the implementation of the Frequency Ratio (FR) model with the aid of GIS tool to assess the contribution of every predisposing factor on landslides and produce a landslide susceptibility map to the area. Approach: A landslide location map of the study area was prepared based on the interpretation of aerial photographs, previous landslide maps and field surveys. In addition, ten relevant thematic maps representing considered factors were extracted from the constructed spatial database. Slope gradient, slope aspect, elevation, distance to road and drainage density, all were calculated from the topographic database; lithology, strata dip map and foliation dip map were generated from the geologic database; lineament density was prepared from Landsat-7 (ETM+) satellite image; and a soil map was prepared from the soil database. Results: relationship between landslides and instability factors was statistically evaluated by frequency ratio analysis. The results suggested that distance to road, lineament density and slope gradient are the most important factors effecting landslides. Frequency ratio values were used to produce the Landslide Susceptibility Index (LSI) with which the study area was divided into five zones of relative landslide susceptibility. Conclusion: The results of the analysis have been validated by calculating the AUC which shows an accuracy of 88.31% in the case of success rate curve and 84.68 % in the case of the prediction rate curve, indicating a high quality susceptibility map obtained from the FR model. The map could be used by decision makers as basic information for slope management and land use planning.
Highlights
Landslides are among the most costly and damaging natural hazards in the mountainous terrains of tropical and subtropical environments, which cause frequently extensive damage to property and occasionally result in loss of life
Over the last three decades, numerous efforts have been devoted by many researchers to develop landslide susceptibility maps
These maps describe areas where landslides are likely to occur in the future and classify those areas into different susceptibility zones from very low to very high susceptible zones according to their susceptibility to landslides
Summary
Landslides are among the most costly and damaging natural hazards in the mountainous terrains of tropical and subtropical environments, which cause frequently extensive damage to property and occasionally result in loss of life. Fine-grained soils, which factors were chosen based on the two above mentioned could be silts or clays, cannot be measured using the studies which were carried out on the study area, the sieves they were classified according to their bibliographical review and from field investigations. Before the analysis was applied, the estimation group was overlaid with thematic data original landslide map was divided randomly into two layers separately the frequency ratio of each sub-set groups, one with 80% (114 cases) of the total factor’s class was calculated in three steps. Dividing the landslide occurrence ratio by the area ratio for each factor’s which were classified into five classes of susceptibility for visual and easy interpretation (Fig. 4). Based on this map, the study area was classified into five classes of susceptibility viz.
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