This study considers landslide susceptibility mapping by means of frequency ratio and artificial neural network approaches using geographic information system (GIS) techniques as a basic analysis tool. The selected study area was that of the Panchthar district, Nepal. GIS was used for the management and manipulation of spatial data. Landslide locations were identified from field survey and aerial photographic interpretation was used for location of lineaments. Ten factors in total are related to the occurrence of landslides. Based on the same set of factors, landslide susceptibility maps were produced from frequency ratio and neural network models, and were then compared and evaluated. The weights of each factor were determined using the back-propagation training method. Landslide susceptibility maps were produced from frequency ratio and neural network models, and they were then compared by means of their checking. The landslide location data were used for checking the results with the landslide susceptibility maps. The accuracy of the landslide susceptibility maps produced by the frequency ratio and neural networks is 82.21 and 78.25%, respectively.

The decision tree is one of the new methods used for the determination of landslide susceptibility in the study area. The Phidim area is selected for the application of this method. The total surface area is 168.07 sq. km, and is located at the eastern part of Nepal. There are total of 10 different data bases used for this study which are; geological formation, elevation, slope, curvature, aspect, stream power index, topographic wetness index, distance from drainage, lineaments, and slope length, and are considered as landslide conditioning factors. Geographical information system (GIS) is used as basic tools and ARC/View is used for the processing data analysis and final map preparation. For the decision tree analysis the PASW 18 (statistical tool) is used to generate values of each factor. According to the results of decision tree, two geological formations; stream power index and slope are found as the most effective parameters on the landslide occurrence in the study area. Using the predicted values, the landslide susceptibility map of the study area is produced. To assess the performance of the produced susceptibility map, the area under curve (AUC) is drawn. The AUC value of the produced landslide susceptibility map has been obtained as 95.9%. According to the results of the AUC evaluation, the produced map has showed a good performance. As to wrap up, the produced map is able to be used for medium scaled and regional planning purposes. DOI: http://dx.doi.org/10.3126/bdg.v15i0.7419 Bulletin of the Department of Geology, Vol. 15, 2012, pp. 69-76

The study was carried out in the vicinity of the Tinau river, Rupandehi, Nepal from July 2011 to June 2012. Ten number of shallow tube wells (STWs) of depths 5.18 m to 7.62 m, four shallow tube wells (STWs) of depths 28.96 m to 36.58 m. from Amawa and Farsatikar Village Development Committees and one dug well (DW) from Butwal Municipality were selected for the purpose of this study. The depth of the STWs was different but many STWs were of 6.09 m deep. The DW was of 18.29 m. The information was collected from the owners during field visit of the sites. A standard questionnaire was prepared and asked to the affected persons. The site observation was done in the dry season as well as in the rainy seasons. It was found that the extraction of riverbed materials from the river channel and the flood plain area has adversely affected the aquatic environment of the Tinau river. Massive extraction of the riverbed materials from this river started after the enforcement of local governance act, and regulation 1999. The income generated from the riverbed materials is quite enough. This is one of the major sources of income generation of DDC Rupandehi and the VDCs attached to this river (from Butwal to Bethari). The depth of the river increased due to extraction activities as a result groundwater table lowered. The STWs having depth of 5.18 to 7.62 m stopped discharging water from the aquifer in the dry season. Similarly DW of Butwal municipality having depth of 18.29 m stopped discharging water at dry season. But the STWs of depths from 28.96 m to 36.58 m. located at the same area/site were not affected by the extraction in the Tinau river. The people, who are residing on the bank of the river Tinau, suffered from drinking water problem because they are using the water from STWs. The effect is directly facing the people of low and medium level having low income generation. The extraction activity is going on and the deficit of water availability in STWs and DW is common in the vicinity of the Tinau river especially in the upstream (from Butwal to Paschim Amawa), whereas there is less effects of riverbed extraction for STWs of depths more than 27.43 m in the same sites.

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A statistical analysis is conducted in this study on the shear strength parameters of fine-grained tills from a series of consolidated undrained triaxial tests performed for a light rail transit project in the City of Toronto. Three different failure criteria are applied: the maximum stress ratio, the maximum deviator stress, and the residual stress. Three methods generate only minimal difference in the shear failure angle and a slight difference in cohesion. The friction angle calculated using the maximum stress ratio method ranges from 18.6 to 35.26 degrees compared with values ranging from 18.5 to 34.26 degrees by the maximum deviator stress method. The undrained shear modulus calculated from one-third and two-third peak deviator stress points generate a wide variation from 2 MPa to 167 MPa with an average value of 34 MPa.