Fluvial sediments of the Siwalik successions in the Himalayan Foreland Basin are one of the most important continental archives for the history of Himalayan tectonics and climate change during the Miocene Period. This study reanalyzes the fluvial facies of the Siwalik Group along the Karnali River, where the large paleo-Karnali River system is presumed to have flowed. The reinterpreted fluvial system comprises fine-grained meandering river (FA1), flood-flow dominated meandering river with intermittent appearance of braided rivers (FA2), deep and shallow sandy braided rivers (FA3, FA4) to gravelly braided river (FA5) and finally debris-flow dominated braided river (FA6) facies associations, in ascending order. Previous work identified sandy flood-flow dominated meandering and anastomosed systems, but this study reinterprets these systems as a flood-flow dominated meandering river system with intermittent appearance of braided rivers, and a shallow sandy braided system, respectively. The order of the appearance of fluvial depositional systems in the Karnali River section is similar to those of other Siwalik sections, but the timing of the fluvial facies changes differs. The earlier appearance (3-4 Ma) of the flood-flow dominated meandering river system in the Karnali River section at about 13.5 Ma may have been due to early uplift of the larger catchment size of the paleo-Karnali River which may have changed the precipitation pattern i.e. intensification of the Indian Summer Monsoon. The change from a meandering river system to a braided river system is also recorded 1 to 3 Ma earlier than in other Siwalik sections in Nepal. Differential and diachronous activities of the thrust systems could be linked to change in catchment area as well as diachronous uplift and climate, the combination of which are major probable causes of this diachronity.

The Siwalik Group constitutes an important archive of Himalayan uplift and related climate changes. Compositional and textural properties of Siwalik sandstones are important parameters for the reconstruction of source lithology, uplift, and the unroofing history of the Himalaya. This study examines fluvial sandstones of the Siwalik Group along the Karnali River, where the large paleo-Kamali River is expected to have flow ed. Modal QFL analysis shows that the sandstones are mainly sub-litharenites or litharenites. Multivariate statistical analysis using Principal Component Analysis (PCA)and the Weltje method shows light variations in sediment composition occur between the Chisapani and Baka Formations. These variatio ns are mainly linked to the source area and tectonics rather than to facies, grain size, or climate. The detrital modes of the sandstones indicate recycled orogen provenance. Comparison of the detrital modes with previous studies indicates that the Higher Himalaya and Lesser Himalaya zones were a common source area throughout the time of deposition. However, subtle changes in feldspar and biotite contents indicate significant supply of detritus derived from the Higher Himalaya after 9.6 Ma.

The depth of the slip surface and thickness of the overburden deposit play a major role in assessing the slope stability of a landslide. Electrical Resistivity Tomography (ERT) survey was carried out in the Taprang Landslide, Kaski district, west- central Nepal to determine subsurface lithological conditions, depth and geometry of the slip surface. Wenner and dipole- dipole arrays were mainly applied in this ERT survey. The electrical resistivity survey revealed that there is a wide range of resistivity value which shows different kinds of layers in the subsurface, and the boundaries between these layers played a significant role to identify the slip surface. The data show mainly three layers from surface to bottom. An upper layer represents the dry to saturated colluvium and sandy gravelly soil (500 to 8000 Ωm), the middle layer is highly –saturated soil with low resistivity value (100–700 Ωm) and unweathered fresh bedrock of schist and quartzite with high resistivity value (1000 to 8000 Ωm) at the bottom layer. The slip surface is considered as depth 25 m at the crown, 10–20 m at the main body part, and below 50 m at the toe and curved in geometry which indicates the rotational type of landslide. Investigation of the slip surface in a landslide using the ERT survey aids to know the slope stability.

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Detailed investigation of Taprang landslide was carried out in order to understand the surface, subsurface lithological information and physical properties of soil by using multi-disciplinary methods such as engineering geological, geophysical and geotechnical studies for the determination of factor of safety for slope stability analysis.  Geological study was carried out by detail mapping of surface geology, soil condition, properties of bedrock and its discontinuities. The geophysical survey (Electrical Resistivity Tomography-ERT) were carried out to know the electrical resistivity of soil for identifying the groundwater table and hence slip surface of the landslide. Geotechnical analysis such as grain size analysis, liquid limit and direct shear test were carried out in order to evaluate soil classification, moisture content, cohesion and the angle of internal friction of soil for knowing the strength the soil. These soil parameters indicate the soil is very low strength. The combination of these results were used for calculating the factor of safety (FoS) by Limit Equilibrium Method (LEM) proposed by Bishop and Janbu methods. The result of factor of safety in the Taprang landslide demonstrates that the slope become stable in drained (dry) condition, remain ultimate stage in undrained (wet) condition and finally failure occurs if applied the seismic load in both drained and undrained conditions.