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Joy Sanyal Priyanka Dasgupta Shinjiro Kanae 《Singapore journal of tropical geography》2020,41(2):284-298
Dam-related downstream adjustments of riverbeds are normally investigated by analysing the trend in sediment supply and high flow events during the pre- and post-dam periods. The required data for existing predictive models is not measured at river gauges, which limits the application of these tools. We derived the frequency of sediment-transporting streamflow events (T*) and upstream sediment supply (S*) in the pre- and post-dam periods with widely available gauged records and predicted changes in the downstream riverbed by adapting an existing model. Ten gauging stations in the Godavari River Basin, India, located downstream of dams, were chosen as study sites. Annually surveyed cross-sections at each site validated the accuracy of the predicted dam-related downstream changes. Then, a regression equation (R2 = 0.75) was established between T*/S* (independent variable) and changes in the downstream bed elevation (dependent variable) for the Godavari Basin. We recommended that similar local empirical equations be formulated for larger river basins. Models of large-scale rainfall-runoff and sediment transport processes that can account for the influence of dams, such as the Soil & Water Assessment Tool, can be paired with the proposed regression equation to estimate dam-related downstream erosion and deposition with globally available data. 相似文献
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Prasanta K. Patro Khasi Raju S. V. S. Sarma 《Journal of the Geological Society of India》2018,92(5):529-532
Magnetotelluric (MT) studies along a few traverses, some cutting across the Western Ghats, during the last few years have provided basic insights into the shallow as well as the deeper electrical structure in the regions near and east of the Western Ghat belt. The MT models broadly show a two layered lithospheric electrical structure with an upper high resistive layer (several thousands of Ωm) and a lower moderately conductive layer (a few tens to a few hundred Ωm). The depth of the interface between the two layers is found to vary from about 120–160 km in the south in the SGT to around 80 km in the north in the northern DVP. Another impressive feature that could be noticed in these electrical models is the presence of well-defined major near vertical crustal conductive feature associated with the region of Western Ghat belt, presumably associated with the tectonic evolution of the Western Ghats. Further, these models also brought out several other well-defined conductors that might be linked to structural features like faults, shear zones, etc., in the region. These conductors pierce through the crustal column and some of these, particularly those oriented in NW-SE direction, i.e., oriented transversely with respect to the ambient compressive stress direction of the Indian shield, assume significance in understanding the seismicity of the region. 相似文献
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Bifurcations of dust acoustic solitary waves and periodic waves in an unmagnetized plasma with q-nonextensive velocity distributed ions are studied through non-perturbative approach. Basic equations are reduced to an ordinary differential equation involving electrostatic potential. After that by applying the bifurcation theory of planar dynamical systems to this equation, we have proved the existence of solitary wave solutions and periodic wave solutions. Two exact solutions of the above waves are derived depending on the parameters. From the solitary wave solution and periodic wave solution, the effect of the parameter (q) is studied on characteristics of dust acoustic solitary waves and periodic waves. The parameter (q) significantly influence the characteristics of dust acoustic solitary and periodic structures. 相似文献
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Dust acoustic double layers are studied in a four component dusty plasma comprising positively and negatively charged dust grains, Boltzmann distributed ions and kappa distributed electrons. The conditions for existence of double layers are studied in detail using Sagdeev’s method. Large amplitude double layers are obtained for a range of values of the plasma parameters. 相似文献
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AbstractData unavailability is the main reason for limited applications of hydrodynamic models for predicting inundation in the developing world. This paper aims to generate moderately high-resolution hybrid terrain data by merging height information from low-cost Indian Remote Sensing satellite (IRS) Cartosat-1 stereo satellite images, freely-available Shuttle Radar Topograph Mission (SRTM) digital elevation model (DEM) data, and limited surveyed channel cross-sections. The study reach is characterized by anabranching channels that are associated with channel bifurcation, loops and river islands. We compared the performance of a simple 1D–2D coupled LISFLOOD-FP model and a complex fully 2D finite element TELEMAC-2D model with the hybrid terrain data. The results show that TELEMAC-2D produced significantly improved simulated inundation with the hybrid terrain data, as compared to the SRTM DEM. LISFLOOD-FP was found unsuitable to work with the hybrid DEM in a complicated fluvial environment, as it failed to efficiently divert water in the branches from the main channel.
Editor D. Koutsoyiannis; Associate editor A. Viglione 相似文献
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Landfill is the most commonly used method for disposal of waste materials since it is one of the least expensive methods. In order to dispose of any hazardous material to a landfill, a liner is used, which protects the underlying land and groundwater since it acts as a barrier to fluid movement. Of the various methods available for providing improved and more effective properties of landfills, methods involving the use of bentonite, cement, lime, gypsum, etc., have been explored in the laboratory. The aim is to overcome the problem and deficiencies of the existing liners. It is observed from the experimental results that the metal concentrations of the input waste solution can be reduced to 80–98% using a soil‐cement admixture, 60–95% using a soil‐gypsum mixture, 45–95% using a soil‐bentonite mixture, 50–90% for soil, 35–80% using a soil‐lime mixture, as liner materials. The permeation rate of different metals through the different soil‐admixture media depends on various factors. A simple mathematical treatment of the phenomenon related to the permeation of liquid through the admixture of the clay and other components has been developed. The experimental results show satisfactory agreement with the predictions. 相似文献
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Temporal analysis of Landsat-TM imageries reveals a saturated state of Kolkata (Calcutta) Metropolitan Area. However, the city has witnessed accelerated growth in real estate construction in recent past. This study applies digital photogrammetry to quantify the changes in Kolkata’s skyline. Recently, released SRTM DEM of 1 Arc Second and a digital surface model derived from WorldView-1 stereo images were used to account for the past and recent surface heights, respectively. Consequently, this paper examines whether the sustained addition in housing capacity has been necessarily driven by a growth in the urban population/number of households. Results show that 40.31% of the area experienced vertical growth, majorly by replacing older dwellings with taller apartment blocks. Further analysis reveals that part of these newly added residences has remained unoccupied as they were purchased by non-resident Indians for using as a second home or was never sold due to recent economic slowdown. 相似文献