Can an annual flood induce changes in channel geomorphology?

The present study has been a pioneering effort examining the role of an annual flood as a potent stimulus inducing changes in channel geomorphology of the Mayurakshi River, India. Twenty cross sections have been considered for the measurement of various hydro-geomorphic attributes of the river in both the pre- and post-flood conditions in 2018. The study sensed an escalating trend for channel width, width/depth ratio, and wetted perimeter while the reverse was also detected for average depth, maximum depth, cross-sectional area, and hydraulic radius. For example, the width/depth ratio recorded an increase of?~?11%, and the hydraulic radius depicted a decrease of?~?8%. Furthermore, channel asymmetry, bed asymmetry and bed relief index experienced a decrease after the flood. The sudden hydraulic impulse during monsoon flood as manifested in velocity, discharge, specific stream power, Reynolds number, Froude number increases the erosivity of the fluid. Besides the hydraulic factors, bank material (massive sandbank susceptible to hydraulic action and mixed bank constituted by alternate bands of sand and silt, and vulnerable to failure by piping action) brings substantial changes in channel morphology. Moreover, anthropogenic interventions such as sand mining are found to play a significant role in channel behaviour. The role of the multiple factors driving the morphological changes of the cross sections has been unpacked using canonical component analysis.

     

SARAL/AltiKa Waveform Analysis to Monitor Inland Water Levels: A Case Study of Maithon Reservoir,Jharkhand, India

In the present study, behavior of the SARAL/AltiKa (Satellite with ARgos and ALtiKa) waveforms over Maithon Reservoir (～65 km² of surface area), Jharkhand, India, has been studied. The estimated water level has been compared with the in situ measurements at hydro-gauging station at the dam site. The problem of minimization of errors in the water level retrieval from AltiKa measurements has been resolved by improvement of the retracking method. A real retracking gate detection algorithm based on statistical analysis harnessing various physical parameters of the waveform has been developed, which has been applied to SARAL/AltiKa waveforms over the Maithon reservoir. Comparing the in-situ measurements with altimetry data (from cycle 1, 19 March 2013 to cycle 12, 8 April 2014) showed that it is crucial to improve the retracking method. Results showed accuracy of water level monitoring increased by nearly 76% by the newly developed waveform retracking algorithm over non-retracked water level. We also compared this new method with the existing ice-1 algorithm and found that with the new method there is improvement of ～27% over ice-1 retracked water level. The correlation coefficient values and root mean square values without retracking, with ice-1 algorithm and with newly developed retracking algorithm were 0.87, 0.91, and 0.95, and 8.12 cm, 2.08 cm, and 1.42 cm, respectively. This shows the proposed retracker performed better than ice-1. The retracking procedure helped in outliers' identification and substitution and with waveform fitting and waveform parameter extraction. This algorithm should have good performance capability for retrieving water level over inland water bodies like Maithon reservoir.     

Prediction of elastic settlement of rectangular raft foundation — a coupled FE–BE approach

A numerical method of analysis is proposed for computation of the elastic settlement of raft foundations using a FEM–BEM coupling technique. The structural model adopted for the raft is based on an isoparametric plate bending finite element and the raft–soil interface is idealized by boundary elements. Mindlin's half-space solution is used as a fundamental solution to find the soil flexibility matrix and consequently the soil stiffness matrix. Transformation of boundary element matrices are carried out to make it compatible for coupling with plate stiffness matrix obtained from the finite element method. This method is very efficient and attractive in the sense that it can be used for rafts of any geometry in terms of thickness as well as shape and loading. Depth of embedment of the raft can also be considered in the analysis. Copyright © 1999 John Wiley & Sons, Ltd.     

Electron-acoustic solitary waves in a relativistically degenerate quantum plasma with two-temperature electrons

Using the Quantum hydrodynamic (QHD) model Korteweg-de Vries (KdV) type solitary excitations of electron-acoustic waves (EAWs) have been examined in a two-electron-populated relativistically degenerate super dense plasma. It is shown that relativistic degeneracy parameter significantly influences the conditions of formation and properties of solitary structures.     

The Work Function Associated with Ultra-relativistic Electron Emission from Strongly Magnetized Neutron Star Surface

Following an extremely interesting idea (Schieber 1984), published long ago, the work function associated with the emission of ultra-relativistic electrons from magnetically deformed metallic crystal (mainly iron) at the outer crust of a magnetar is obtained using relativistic version of Thomas–Fermi type model for electron distribution around the nuclei in this region. In the present scenario, surprisingly, the work function becomes anisotropic; the longitudinal part is an increasing function of magnetic field strength, whereas the transverse part diverges.     

Comparison of two forest types using adeos 1-polder data over west coast of India

Parametric kernel-based models for Bi-directional Reflectance Distribution Function (BRDF) of vegetated land surfaces attempt to describe the BRDF as a linear superposition of a set of kernels describing basic angular shapes. The kernels and associated model coefficients are derived as approximations to the underlying theories of radiative transfer as well as geometric-optical scattering within vegetation canopies. In the present study, five kernels viz. Ross-Thick, Li-Sparse, Ross-Thin, Li-Dense and Roujean geometric-optical (GO) kernels along with a purely empirical model were examined for their suitability in describing the angular characteristics of two forest types (semi-evergreen and deciduous) during November 1996-March 1997 using ADEOS-1 POLDER data. The statistically significant kernels and their combinations with respect to red and NIR (near infra-red) wavelengths were determined using correlation analysis. Atmospherically corrected POLDER measured reflectances at red and NIR wavelengths were regressed with different kernels and their combinations. It is found that the best fitting volume and GO kernel combinations depend on forest type, wavelength and date.     

Landscape Dynamics in North East Region of India (Meghalaya State) Using Spatial Decision Tree Model

Abstract

India has figured with two hotspots ‐ the Western Ghats and the Eastern Himalayas ‐ in an identification of 8 ‘hottest’ biodiversity hotspots (Myers et. al. 2000). The Meghalaya state (study area) in North Eastern India lies within the “Indo‐Burma” area, which is one of the 8 ‘hottest’ biodiversity hotspots. Timber extraction, the age‐old practice of shifting cultivation and mining has been a major cause of extensive changes in this landscape. Human induced disturbance differs from natural disturbance especially in extension, severity and frequency. Spatial presentation of landscape dynamics can be used to infer disturbance regimes horizontally. Disturbance regimes are mostly dominated by landuse practices in Meghalaya and these landuse practices are important contributors for overall interpretation of ecological processes operating within the landscape. In this scenario, the development of models to study landscape dynamics using remote sensing and GIS would be of great importance to ecologists. In this paper, we make an attempt to characterize landscape dynamics using a decision tree based approach. The varying impacts of human interventions reflected in three zones at landscape level have been brought out in the present study. The physiographic zones of Meghalaya (viz. Garo hills, Khasi hills and Jaintia hills) manifest different landscape characteristics and present varying degree of degradation status. Garo hills, experiences maximum shifting cultivation and has shown highest dynamism in the study area followed by Jaintia and Khasi hills. Characterization of landscape dynamics is important in the perspective of decision makers and policy makers in order to prioritize conservation strategies, so that urgent and necessary action can be taken.     

Analysing spatio-temporal footprints of urbanization on environment of Surat city using satellite-derived bio-physical parameters

Our study examines the relationships among various environmental variables in Surat city using remote sensing. Landsat Thematic Mapper satellite data were used in conjugation with geospatial techniques to study urbanization and correlation among satellite-derived biophysical parameters namely, normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI), normalized difference water index (NDWI), normalized difference bareness index (NDBaI) and land surface temperature (LST). A modified NDWI (MNDWI) was used for extracting areas under water. Land use/land cover classification was performed using hierarchical decision tree classification technique using ERDAS IMAGINE Expert classifier with an accuracy of 90.4% for 1990 and 85% for 2009. It was found that city has expanded over 42.75 sq.km within two decades. Built-up, fallow and sediment land use classes exhibited high dynamics with increase of nearly 200% and 50% and decrease of 55% respectively from 1990 to 2009. Vegetation and water classes were less dynamic with 20% decrease and 15% increase. The transformation of land parcels from vegetation to built-up, vegetation to fallow and fallow to built-up has resulted in increase of LST by 5.5 ± 2.6°C, 6.7 ± 3°C and 3.5 ± 2.9°C, respectively.     

Study of drainage profiles in Jharia Coalfield,eastern India from aerial photographs: Implication for land use planning

Drainage analysis of an area through aerial photographs helps a lot in knowing its soil textrue, mainly its porosity, permeability, grainsize and compactness. These observations may be used as a guide for land use planning over the area. Studies have been conducted in Jharia Coalfield through scanning of acrial photographs to know the textural characters of soil/rock cover over the area. Nature of valley profiles have been studied in detail. The overall drainage pattern and drainage texture have also been studied. The observation have been used to infer about the textue of the materials (rock/soil) traversed by the drainage lines in the region. The observations suggest that the major part of the field is covered by materials of moderate cohesiveness with good porosity, permeability and recharge capacity. These informations have been used as critical inputs for future land use planning in the area.     

Area Change and Thickness Variation over Pensilungpa Glacier (J&;K) using Remote Sensing

Accurate representations of the Earth’s surface in the form of digital elevation models (DEMs) are essential for a variety of applications in glaciological and remote-sensing research. In the present study area change and thickness variation over Pensilungpa glacier was attempted using remote sensing approach. It can be remarked that a net loss of 9.23 sq. km. which is 38% of the glacier area mapped in 1962 indicate a drastic change over the glacier area during 1962–2007. Estimation of glacier thickness change on Pensilungpa glacier based on ASTER DEM (2003) and Survey of India (SOI) contour based DEM (1962) indicated increase in the glacier elevation in the accumulation zone mainly by 30 to 90 m and similar reduction by 30 to 90 m in the ablation zone.