Frequency Ratio Analysis Research Articles

Landslide Susceptibility Assessment using Frequency Ratio Model Applied to an Area along the E-W Highway (Gerik-Jeli)

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.

Frequency ratio analysis of mass movements in the Xiangxi catchment, Three Gorges Reservoir area, China

In 2003, the Three Gorges Project (TGP, China), currently the world's largest hydro- electric power plant by total capacity, went into operation. Due to large-scale impoundment of the Yangtze River and its tributaries and also due to resettlement, extensive environmental impacts like land use change and increase of geohazards are associated with the TGP. Within the Yangtze Project, we investigate these effects for the Xiangxi (香溪) catchment which is part of the Three Gorges Reser- voir. The aim of this study is to evaluate the susceptibility for mass movement within the Xiangxi River backwater area using geographic information system (GIS). We used existing mass movements and the conditioning factors (geology, elevation, slope, curvature, land use, and land use change) for analyzing mass movement susceptibility. Mass movements and geology were mapped in the field to establish a mass movement inventory and a geological map. Land use and digital elevation model (DEM) were ob- tained from remote-sensing data. We determined the relation between mass movements and the condi- tioning factors by using the frequency ratio method and found strong relation between mass move-