Characterization of suspended sediment in Meltwater from Glaciers of Garhwal Himalaya

Glacierised basins are significant sources of sediments generated by glacial retreat. Estimation of suspended sediment transfer from glacierised basins is very important in reservoir planning for hydropower projects in Himalaya. The present study indicates that storage and release of sediment in proglacial streams may categorise the pattern of suspended sediment transfer from these basins. Assessment of suspended sediment concentration (SSC), suspended sediment load (SSL) and yield has been undertaken for Dunagiri Glacier basin located in Garhwal Himalaya (30^o33'20”N, 79^o53'36”E), and its results are compared with the Gangotri and Dokriani glaciers sharing close proximity. Out of the total drainage basin area, about 14.3 % of the area is glacierised. Data were collected for five ablation seasons (1984–1989, barring 1986). The mean daily SSCs for July, August and September were 333.9, 286.0 and 147.15 mg/l, respectively, indicating highest concentration of mean daily suspended sediment in July followed by August. SSL trends were estimated to be 93.0, 57.0 and 21.3 tonnes. About 59% of the total SSL of the melt period was transported during the months of August and September. Sediment yield for the study basin was computed to be 296.3 t km^?2 yr ^?1. It is observed that the cumulative proportion of SSC precedes the discharge throughout the melt season except in the year 1987. Release of SSL in terms of total load is less in the early part of melt season than in the later stage as compared to that of discharge. Diurnal variations in SSC reach their maximum at 2400 h, and therefore, SSC was found to be high during night (2000–0400 h). There was a good relationship between SSC and SSL with discharge for the ablation seasons (1988 and 1989). Mean monthly SSC and mean monthly SSL provide a good exponentional relationship with mean monthly temperature. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessing the state of homogeneity,variability and trends in the rainfall time series from 1969 to 2017 and its significance for groundwater in north-east India

Natural Hazards - Rainfall is the key climatic variable, on which water availability, food security and livelihood depend, especially in an agrarian society like the northeast region of India. It...     

Assessment of tunnel instability—a numerical approach

This paper outlines the application of numerical modeling to predict deformation and stability of tunnel to be excavated in Bansagar, M.P., India. To meet the ever-increasing demand of transportation, energy, and other infrastructure projects, a large volume of rock tunneling is being carried out throughout the world. The geotechnical properties along the route of the 1,800-m long tunnel in the Bansagar region of India have been studied. The rock mass rating and rock mass quality systems were employed for empirical rock mass quality determination. Numerical analysis for the stress–strain distribution of the tunnel excavation and support systems was also carried out. In order to simulate the excavation of tunnel (NATM) at a depth of 150 m below the ground , a series of finite element analyses using Mohr-coulomb elasto-plastic constitutive model has been carried out using PLAXIS 2D. The stability of tunnel has been analyzed, and stress pattern have been discussed.     

Implication of drainage basin parameters of Chhoti Gandak River,Ganga Plain,India

The drainage basin parameters of the groundwater-fed Chhoti Gandak River originating in the terai area of the Ganga Plain were analyzed using topographical sheets, satellite data, and field documentation with emphasis to its implication for flood mitigation and recharging of groundwater. The analyses indicate dominance of first order streams, gentle slope gradient, low surface run-off, low sediment production, high infiltration rate, and low value of basin relief. The low water storage capacity, spreading of water and concentration of peak discharge in the distal part of the river basin explain that whenever precipitation is high in the catchment area there is flood in the distal part of the basin. The bifurcation ratio value (4.34) of this basin describes that the drainage is carved naturally by slope and local relief and not influenced by geological structures like lineaments and faults.     

Natural hazards in the Ghaghara River area, Ganga Plain, India

The Ganga Plain is one of the most densely populated regions of the world due to its fertile soil and availability of water. The rivers of this plain are the lifeline for millions of people of this vast alluvial plain. All rivers of this plain are characterized by narrow channel confined within wide valley. Continuously increasing pressure of population on this plain has led to the intensification of settlement even into the valley of the river. This unplanned expansion has enhanced the damage due to flooding during high-discharge period and lateral erosion during low-discharge period. Flooding and lateral erosion are identified as fluvial hazards in the Ghaghara River area. Extensive studies have been carried out on flooding, but not much attention has been paid to the phenomenon of lateral erosion. However, it has been observed that lateral erosion is an independent fluvial hazard that operates during low-discharge period. Low degree of compaction due to the presence of sandy and silty facies in the river valley deposits, mass movement, palaeocurrent pattern, and fractures initiates and enhances the lateral erosion. The present paper deals with the fluvial hazards in the Ghaghara River area.     

Characteristics of sea-cliff erosion induced by a strong winter storm in the eastern Mediterranean

Changes in sea-cliff morphologies along the 30-km-long Sharon Escarpment segment of Israel's weakly cemented Mediterranean eolianite cliff line were analyzed to gain quantitative insights into erosion characteristics associated with a high-energy winter storm (10–20 year return interval). Ground-based repeat LiDAR measurements at five sites along the cliff line captured perturbations of cliff stability by basal wave scouring during the storm, subsequent post-storm gravity-driven slope failures in the cliff face above, and return of the system to transient stability within several months. Post-storm erosion, which amounted to 70% of the total volume of cliff erosion documented, resulted in dramatic local effects of up to 8 m of cliff-top retreat. And yet, at the larger scale of the 30-km cliff line examined, erosion during the storm and the year that followed affected less than 4% of the cliff length and does not appear to be above the average cliff-length annual erosion implied by previously published decadal-scale retreat rates along this sea cliff. Our results do not support a direct association between strong storm events and elevated erosion and retreat at the cliff-line scale.     

Influence of rooftop telecommunication tower on set back-step back building resting on different ground slopes

In the hilly region due to scarcity of the plain area, buildings like set back-step back are more often used and also as a big surge in the telecommunication industries, rooftop tower adaptation is very common story nowadays. In the present study an analogy has been drawn to find out the influence of the rooftop telecommunication tower on the setback-step back building resting on ground at 20° and 30° slopes. A dynamic analysis has been performed and compared on the 4 legged angled section telecommunication tower which is located on the roof top of set back-step back building by varying positions of tower with the existing host structure built up on ground slope of 20° and 30° in both directions(X and Y).     

Detecting thermal boundary control in surface flows from numerical dynamos

The geomagnetic field and secular variation exhibit asymmetrical spatial features which are possibly originating from an heterogeneous thermal control of the Earth's lower mantle on the core. The identification of this control in magnetic data is subject to several difficulties, some of which can be alleviated by the use of core surface flow models. Using numerical dynamos driven by heterogeneous boundary heat flux, we confirm that within the parameter space accessible to simulations, time average surface flows obey a simple thermal wind equilibrium between the Coriolis and buoyancy forces, the Lorentz, inertial and viscous forces playing only a secondary role, even for Elsasser numbers significantly larger than 1. Furthermore, we average the models over the duration of three vortex turnovers, and correlate them with a longer time average which fully reveals the signature of boundary heterogeneity. This allows us to quantify the possibility of observing mantle control in core surface flows averaged over a short time period. A scaling analysis is performed in order to apply the results to the Earth's core. We find that three vortex turnovers could represent between 100 and 360 years of Earth time, and that the heat flux heterogeneity at the core-mantle boundary could be large enough to yield an observable signature of thermal mantle control in a time average core surface flow within reach of the available geomagnetic data.