Geotechnical characterization and analysis of rainfall—induced 2009 landslide at Marappalam area of Nilgiris district,Tamil Nadu state,India

Landslides are frequently occurring natural hazards in Nilgiris district of Tamil Nadu, India, particularly during monsoon season. The present study describes the geotechnical characterization and analysis of rainfall-induced landslide that occurred at Marappalam location of Nilgiris district on November 10, 2009. The detailed investigation comprises mapping of landslide, topographical survey, field and laboratory investigations, characterization of soil and rock, and numerical analysis. Field study comprises borehole and geophysical investigations. Detailed laboratory investigation was performed to identify index and engineering properties of soil and rock. Based on the results obtained from field and laboratory investigations, the generalized subsoil profile of Marappalam slope has been plotted. The investigations revealed that loose and soft soil layer with low permeability and plasticity interspersed with boulders could be the main source of debris flow. Scanning electron microscopic analysis and x-ray diffraction analysis were performed to study the influence of weathering on slope failure. Failure mechanism of Marappalam 2009 landslide was identified from the numerical analysis performed using landslide simulation program LS-RAPID. The analysis revealed that the 5-day antecedent rainfall (303 mm) and intense rainfall on 10th November 2009 (405 mm) saturate the slope due to infiltration of rainwater. This leads to a decrease in the matric suction and subsequent development of positive pore water pressure, which in turn reduces the shear resistance of the soil along with shear displacement, and resulted in a progressive failure.     

An overview on geochemistry of Proterozoic massif-type anorthosites and associated rocks

A critical study of 311 published WR chemical analyses, isotopic and mineral chemistry of anorthosites and associated rocks from eight Proterozoic massif anorthosite complexes of India, North America and Norway indicates marked similarities in mineralogy and chemistry among similar rock types. The anorthosite and mafic-leucomafic rocks (e.g., leuconorite, leucogabbro, leucotroctolite, anorthositic gabbro, gabbroic anorthosite, etc.) constituting the major part of the massifs are characterized by higher Na₂O + K₂O, Al₂O₃, SiO₂, Mg# and Sr contents, low in plagioclase incompatible elements and REE with positive Eu anomalies. Their δ ¹⁸O‰ (5.7–7.5), initial ⁸⁷Sr/⁸⁶Sr (0.7034–0.7066) and ɛ _Nd values (+1.14 to +5.5) suggest a depleted mantle origin. The Fe-rich dioritic rocks occurring at the margin of massifs have isotopic, chemical and mineral composition more close to anorthosite-mafic-leucomafic rocks. However, there is a gradual decrease in plagioclase content, An content of plagioclase and X_Mg of orthopyroxene, and an increase in mafic silicates, oxide minerals content, plagioclase incompatible elements and REE from anorthosite-mafic-leucomafic rocks to Fe-rich dioritic rocks. The Fe-rich dioritic rocks are interpreted as residual melt from mantle derived high-Al gabbro melt, which produced the anorthosite and mafic-leucomafic rocks. Mineralogically and chemically, the K-rich felsic rocks are distinct from anorthosite-mafic-leucomafic-Fe-rich dioritic suite. They have higher δ ¹⁸O values (6.8–10.8‰) and initial ⁸⁷Sr/⁸⁶Sr (0.7067–0.7104). By contrast, the K-rich felsic suites are products of melting of crustal precursors.     

Role of hydrological regime and floodplain sediments in channel instability of the Bhagirathi River,Ganga-Brahmaputra Delta,India

Abstract

This research deals with the surface dynamics and key factors – hydrological regime, sediment load, and erodibility of floodplain facies – of frequent channel shifting, intensive meandering, and lateral instability of the Bhagirathi River in the western part of the Ganga-Brahmaputra Delta (GBD). At present, the floodplain of the Bhagirathi is categorized as a medium energy (specific stream power of 10–300 W m^?2), non-cohesive floodplain, which exhibits a mixed-load and a meandering channel, an entrenchment ratio >2.2, width–depth ratio >12, sinuosity >1.4, and channel slope <0.02. In the study area, since 1975, four meander cutoffs have been shaped at an average rate of one in every 9–10 years. In the active meander belt and sand-silt dominated floodplains of GBD, frequent shifting of the channel and meander migration escalate severe bank erosion (e.g. 2.5 × 10⁶ m³ of land lost between 1999 and 2004) throughout the year. Remote sensing based spatio-temporal analysis and stratigraphic analysis reveal that the impact of the Farakka barrage, completed in 1975, is not the sole factor of downstream channel oscillation; rather, hydrogeomorphic instability induced by the Ajay–Mayurakshi fluvial system and the erodibility of floodplain sediments control the channel dynamics of the study area.     

Impact of the Trans-Himalayan Landslide Lake Outburst Flood (LLOF) in the Satluj catchment, Himachal Pradesh, India

Landslide Lake Outburst Floods (LLOFs) are common in the Himalayan river basins. These are caused by breaching of lakes created by landslides. The active and palaeo-landslide mapping along the Satluj and Spiti Rivers indicate that these rivers were blocked and breached at many places during the Quaternary period. In the present article, we document LLOFs during 2000 and 2005 caused by the breaching of landslide lakes created in the Trans-Himalayan region along the Satluj River and Paree Chu (stream), respectively, both in the Tibetan region of China and its impact on the channel and infrastructure in the Kinnaur district of Himachal Pradesh, India. It has been observed that the loss of life and property due to these LLOFs is directly related to the disposition of the Quaternary materials and the different morphological zones observed in the area.     

Experimental study of fracture processes in rock

Summary The Fracture process zone in compact tension specimens of Indiana limestone was investigated to study its effect on the fracture mechanics parameters in such materials. Specimens were tested up to the peak load, and propagation of the crack from a preexisting notch was monitored. Experiments were designed to study the two features of the fracture process zone in rocks: ligament connections and microcracking.To observe this zone with high sensitivity and accuracy, laser interferometry methods were adopted. Holographic Interferometry was used to observe initial crack propagation. To obtain more quantitative measurements of the displacement field, in realtime, the recently developed technique of electronic speckle pattern interferometry was applied. This technique can provide continuous video recording of the interferometric fringe pattern, depict the evolution of the fracture process, and measure profiles of crack opening displacements.The macroscopic observations of full-field displacement by the laser techniques were supplemented by post mortem observation of the fracture region under a scanning electron microscope. Regions around the crack were studied after the test for possible presence of microcracks.An interactive finite element code was used to compute the stress intensity factors of the propagating crack-tip and displacements. Finite element computations were used to evaluate the effect of the process zone on crack propagation.     

Private non-degree practitioners and spatial access to out-patient care in rural India

Most rural areas in the developing countries lack access to qualified out-patient (OPD) care. The gap in health services provision arises, due to lack of qualified doctors and is oftentimes filled by unqualified doctors who are also known as private non-degree practitioners (PNDPs). Despite their dominance, their presence is often neglected in access to health care studies. This leaves a scenario which lacks informal, but predominant, care. This paper uses a mix-method approach, combining exhaustive quantitative census of all health care providers along with location details in Geographic Information System to address the accessibility to PNDP. Longitudinal quantitative as well as spatial surveys were conducted for 3 years (2010, 2012 and 2013) in districts of Pratapgarh and Kanpur Dehat in state of Uttar Pradesh and Vaishali in Bihar state. The results of this study show that PNDPs account for 25 % of the all health care providers active across the study areas. The PNDPs are active in a radius of 2–5 km and are main workforce for the OPD care. Considering all health care providers PNDPs provide best potential accessibility to OPD care. If the PNDPs are removed from the scenario; remote areas will be the most affected ones, leaving them with almost no OPD care.     

Finite element modelling of landslide prone slopes around Rudraprayag and Agastyamuni in Uttarakhand Himalayan terrain

Himalayan mountain chains are neo-tectonically active and significantly susceptible to frequent geohazards like landslides, earthquakes, cloudburst and flash floods, etc. Himalayan slopes are characterized by highly fractured, jointed and sheared rock mass. This affects the strength of the rocks and thus largely influences the stability characteristic of slopes which have been aggravated by human intervention. The ongoing developmental activities, particularly in the last two decades, are responsible for large-scale destabilization of slopes. In rugged terrain, safer designs along hill-cut roads must be ensured. Despite extensive geotechnical works for slope stabilization done in the Himalayan range, slope sections evolve due to various natural and man-made factors are need to be understood in greater details. Proper evaluation and treatment were done on the cut slopes that are severely affected during Kedarnath disaster of June 2013. One of such roads is national highway from Rudraprayag to Gaurikund near Kedarnath. In this study, the stability of vulnerable road cut slopes from Rudraprayag to Agastmuni was investigated. Three key road cut slopes were considered. Finite element analysis was conducted using PLAXIS simulator. Factors of safety, stress, strain, horizontal and vertical displacement have been determined for each slope. The most unstable slope had a factor of safety (FoS) equal to 0.935, while the most stable slope had FoS equal to 2.56. Outcomes from simulation are in good agreement with the prevailing field conditions. Slope stability evaluation must be performed to ensure better safety and to achieve disaster mitigated design.     

An assessment of Dungale landslide using remotely piloted aircraft system (RPAS), ground penetration radar (GPR), and Slide & RS2 Softwares

Natural Hazards - In the present study, slope stability analysis was done using limit equilibrium method and finite element method of the Dungale landslide situated in the NW Himalaya along Tons...     

Climate change impact in the Western Himalaya: people’s perception and adaptive strategies

The Himalaya represents a vast mountain system and globally valued for its significant role in regulation of global as well as regional climate that has direct impact on biodiversity and ecosystem services crucial for sustenance of millions of people in Himalaya and adjoining areas. However, mountain regions worldwide are impacted by climate change and at the same time represent distinctive area for the assessment of climate related impacts. Climate change impacts in Himalayan region have its implications on food production, natural ecosystems, retreat of glacier, water supply, human and animal health and overall human well being. The livelihood and food security of the people inhabited in region largely depend on climate sensitive sectors i.e. agriculture, livestock, forestry and their interlinkages with each other, and has the potential to break down food and nutritional security as well as livelihood support systems. People’s perception and understanding of climate can be an important asset when it comes to adaptation to climate change impact; however it is not taken into consideration for the development of policy design and implementation of modern mitigation and adaptation strategies by governments and other civil society organizations. The knowledge of local people and farming communities for rural landscape management and sustainable use of bioresources is gaining credence as a key strategy to cope up with the climate change. Therefore, the present study analyzes the indigenous knowledge of local people and their perceptions on climate change, and also documented adaptation approaches at local level in mountain ecosystem of western Himalaya. The study could be useful to policy makers to design appropriate adaptation strategies to cope up with the impacts of climate change.     

Gold Mineralization in Kottathara Prospect, Attappadi Valley, Kerala, India: a Preliminary Appraisal

The Kottathara gold prospect of Attappadi Valley in Kerala is located within the Southern Indian Granulite Terrain comprising charnockite and gneisses with enclaves of high-grade supracrustals. The gold mineralization associated with the basic members of the Attappadi supracrustals and the quartz veins traversing them are confined within the Bhavani Shear Zone. Primarily the gold-quartz lode is emplaced in rheologically preferred zones along the contact of the basic members with the enclosing gneisses subsequent to a period of retrogression and shearing. Ore-mineralogical studies reveal that gold got remobilized and this remobilization is identified with the regional Bhavani Shear. SEM studies indicate that gold occurs in free state and also within sulphides especially pyrite. Variation in grain morphology is clearly discernible in gold occurring within oxidised and in non-oxidised zones.Sequencing of deformational events with associated emplacements of known ages suggests the age of gold mineralization of Attappadi area as between 2 Ga. and 2.5 Ga. The secondary mobilization has to be <2.0 Ga or younger possibly of younger Pan-African age related with the Moyar-Bhavani Shear System. The inherent gold content of the komatiitic metapyroxenites together with the auriferous quartz lodes assigns a lithological control on gold mineralisation. Subsequent folding and remobilization due to the regional shear constrained the geometry of the lode zones implying structural control.