H. Baboli-moakher; K. Shirani; A. R. Taghian
Abstract
Catchments are natural systems in which natural phenomena like landslides are considered as natural disasters. As a chaos factor, they have a main role in forming unstable condition, tackling energy, accelerating erosion and generating sediment. So factors causing slope instability are reaction of the ...
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Catchments are natural systems in which natural phenomena like landslides are considered as natural disasters. As a chaos factor, they have a main role in forming unstable condition, tackling energy, accelerating erosion and generating sediment. So factors causing slope instability are reaction of the system to positive feedback. This study aims to employ theory of natural system chaos, in the form of Shannon entropy index, to find the factors causing landslide and its hazard zonation in Fahlian basin. First, input layers including geology, rainfall, slope, aspect, land use, distance to river, distance to fault, and elevation were digitized using GIS techniques. Then occurred landslides were detected using satellite images and field study. Landslide hazard zonation based on defined weights of each parameter was generated. In order to run model and study its accuracy, receiver or relative operating characteristic (ROC), was used with 70 and 30 per cent of data as training and test, respectively. Results show that slope and aspect have the maximum effect on landslide occurrence with ultimate weight of 0.662 and 0.308, respectively. Landslide susceptibility zonation map show that more than half of study area (56.97 percent) have very high to high susceptibility. Disaggregation of areas with SCAI method show the high accuracy of the model in detection of area with average, low and very low susceptibility. Frequency ratio of hazard classes deals with high accordingly, area under curve (AUC) of ROC was estimated 0.87 with 0.026 standard deviation which is known as very good accuracy of model.
M Mansouri; K Shirani; A. Ghazifard; S. N. Emami
Abstract
In this research, two probabilistic methods (i.e., weight of evidence and index of entropy models) are used to perform landslide hazard zonation mapping in Doab Samsami region in Chaharmahal and Bakhtiari Province. For this purpose, ten landslide-conditioning factors (i.e., slope gradient, slope direction, ...
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In this research, two probabilistic methods (i.e., weight of evidence and index of entropy models) are used to perform landslide hazard zonation mapping in Doab Samsami region in Chaharmahal and Bakhtiari Province. For this purpose, ten landslide-conditioning factors (i.e., slope gradient, slope direction, precipitation, gravity acceleration, distance to roads, distance to streams, distance to faults, distance to residential areas, lithology and land use) are used. A landslide inventory map was prepared using the known landslides, Google Earth images, and field observations. The landslide hazard map was prepared taking into account the weights calculated by both models and computerized in ArcGIS Software. The SCAI and the area under the curve (AUC) of receiver operating characteristic (ROC) were used to evaluate them. The results of both models imply a good prediction of landslide hazard in the studied area. They indicate that precipitation, lithology and land use have the greatest impacts on the landslides occurred in the Doab Samsami region, respectively, and that both models are appropriate for the landslide hazard mapping. The validation results using 30% of the landslide points showed that in weight of evidence model AUC is 79% and was able to predict the landslides slightly better than the index of entropy method in which AUC was 73%. The maps produced by these models can be useful for regional spatial planning and for land use planning.
K Shirani; A Seif; A Nasr
Abstract
Regarding their nature and their variety, and hazards that landslides have for humans life and properties, landslides have always been the center of attention and study by scientist from different fields of study such as: geology, engineering geology, geomorphologies, these phenomena are a complex activity ...
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Regarding their nature and their variety, and hazards that landslides have for humans life and properties, landslides have always been the center of attention and study by scientist from different fields of study such as: geology, engineering geology, geomorphologies, these phenomena are a complex activity and different factors and variables could be effective in this occurrence, numerous studies have been done to recognize the effective factors, classification, zooming and modeling. Accordingly, we have tried to study the landslides in Kahredan basin in northern part of Semirom, DenaMountain in Zagros zone suburban area in Esfahan province and provide a landslide hazard zonation map by using the statistical method and the hazard map which has the most accuracy and precision will be selected. So finally we specify the order of effective parameters in landslides. According, by selecting following six parameters: slope aspect, lithology, land use, rainfall and distance from drainage, we provided the distribution of landslides map by using following four methods.
Information value, linear regression, discriminate analysis and area density. The best landslide hazard zonation map has been statistical method of information value which is capable of using in planning and urban developments. Effective parameters in landslides according to their importance are, lithology, distance from drainage, land use, slope and rainfall.