A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Maiti, Ramkrishna
- Stress on Embankment as Negative Feedback in the System of Reclaimed Sundarban-A Case Study along the Raimangal
Authors
1 Dept. of Geography and Environment Management, Vidyasagar University, Paschim Medinipur, West Bengal, 721102, IN
Source
Indian Science Cruiser, Vol 24, No 1 (2010), Pagination: 24-27Abstract
In an environment of active delta building through the interaction of hydrologic, atmospheric and tidal processes, the intervention through erection of embankments closer to the tidal channels for reclamation of the inter-tidal areas sets a serious impact on system dynamics which are adjusted through embankment breaching. High tide becomes swifter and higher indicating the potentiality of overtopping and erosion. This reclamation makes the channels hydraulically ‘unfit’ and those are gradually narrowed down. It provokes in complete closure of the interior channels through construction of series of longitudinal and transverse embankments and completes occupying of the channel areas for fishing, cultivation and habitation. The increased hydraulic head of 0.43m allows an additional 167309 m3 more flood water to enter into the reclaimed area through a representative breach of 7.65m plan length of curved breach crest, 4.32m height of the tide level from the base of embankment and 4.86m hydraulic head on breach crest at breach channel centerline. Geotechnical analysis shows that the embankment materials may get stability at the repose angle of 2°, but in many cases, the slope on the embankment exceeds 50° that indicates absolute internal instability of the materials.Keywords
Reclamation, Embankment, Tidal Asymmetry, Drainage Decay, Breaching.
- An Investigation for Methodological Framework to select Grass Roots for Controlling Rill and gully Erosion in Lateritic Area in West Bengal, India
Authors
1 Department of Geography & Environment Management, Vidyasagar University, Medinipur - 721102, West Bengal, IN
2 Department of Botany, Saldiha College, Saldiha-722 173, Bankura, West Bengal, IN
Source
Indian Science Cruiser, Vol 25, No 2 (2011), Pagination: 32-37Abstract
Traditional vegetation techniques to control rill-gully erosion rely mainly on the effects of above ground biomass; whereas little attention has been given to the role of below ground biomass i.e. ischolar_mains system. Yet, in a context where above ground biomass may temporally or specially disappear (e.g. due to temperature or over grazing), ischolar_mains can play an important role in soil erosion rates. This paper presents a methodology to assess the suitability of grass ischolar_mains for rill-gully erosion control and its application to 8 grass species, representative for a semi-arid lateritic rolling environment in western part of West Bengal, India. In this analysis determination of suitable grass species for controlling concentrated flow erosion is based on a multi-criteria analysis. First, two main criteria are determined, i.e. (i) the high potential of grass ischolar_mains to prevent incision by concentrated flow erosion, (ii) the potential of resist to bending by water flow. Then an indicator was used to assess the scores for the two criteria. In total three indicators are selected, i.e. RD, RLD, and RAR. The scores for the indicators are represented on triangulation diagrams. Among the experimental grass species, Eragrostis cynosuroides grass ischolar_mains are found to be more suitable than other species for rill-gully erosion control in lateritic badland topography.
Keywords
Lateritic Soil, Rill-Gully Erosion, Soil Conservation, Grass Roots.- Local Scour at and Around Vertical Hydraulic Structure - A Case Study Around the Piers of Bridges on Rupnarayan River, WB
Authors
1 Dept. of Geography and Environment Management, Vidyasagar University, Midnapur-721102, West Bengal, IN
Source
Indian Science Cruiser, Vol 26, No 6 (2012), Pagination: 38-46Abstract
Local scouring is the lowering of the riverbed level by water erosion due to separation of flow and development of vortices around hydraulic structures. Excavating and carrying away materials from the bed and banks of streams and from around the hydraulic structures cause failure of riverine structures throughout the world especially during the river floods. The present study incorporates the review of the existing literature on scour with emphasis on the understanding of the mechanism of scouring, prediction of scour depth, correlation of local scour and sediment transport capacity and reduction techniques of local scour around vertical piers. Actual scour depth data have been collected from the piers of bridges near Kolaghat region on Rupnarayan River. The expected scour depth is calculated based on different scour controlling parameters for the same. Dou (1997) established the relationship between local scouring and effective sediment transport capacity (STC). Many researchers have employed different techniques to predict the maximum depth and diameter of scour hole. In a few studies, procedures to reduce the scour depth have been used by making use of splitter plates and collars on the piles. Helical wires or cables wrapped spirally around the pile resembling a threaded pile have also been used to reduce the scour. With the use of different special techniques, the scour depth has been reported to reduce by modifying the flow field near the bridge elements. The Lacey-Inglis method (1992, 1944) is used in India for estimation of the design scour depth around hydraulic structures. Prediction of scour depth and protecting it is very difficult due to many uncertainties associated with it and sometimes become very costly. More studies and investigations are still required to predict the scour depth effectively and also to find cost-effective ways to protect the scour.
Keywords
Local Scouring, Hydraulic Structures, Sediment Transport Capacity, Scour Depth, Splitter Plates, Collars, Threaded Piles.- Application of The Factor-Based Approach to Evaluate Landslide Hazard in The Shiv-Khola Watershed of Darjiling Himalaya
Authors
1 Department of Geography, Raja N.L.Khan Women’s College, Paschim Medinipur, West Bengal, 721102, IN
2 Department of Geography and Environment Management, Vidyasagar University, Paschim Medinipur, West Bengal, 721102, IN
Source
Indian Science Cruiser, Vol 27, No 2 (2013), Pagination: 19-26Abstract
The quantitative analysis of landslide inducing attributes like slope, amplitude of relief, drainage density, upslope contributing area, topographic index, and land use is of great significance for the scientific management of mountain watershed. Preparation of Landslide Zonation Map is an important technique which figure out spatial distribution of landslide and helps to take site specific proper remedial measures in a rational manner. In the present study the interaction of different factors are studied separately and ultimately final coordination is made through Landslide Potentiality Index Value (LPIV) and Landslide Susceptibility Index Value (LSIV). For the preparation of the hazard zonation map of the Shivkhola watershed, grid/cell wise weighted index value (WIV) is assigned for each and every classes of individual attributes on the basis of the magnitude of landslide potentiality index value. Landslide Susceptibility Index Value (LPIV) is the outcome of the cumulative total of all grid/cell wise assigned WIV. Lastly, a statistical analysis has been made using Origin Software (8.00) to bring out the relationship between LSIV (Y) and individual landslide inducing factors (X).-The analysis states that 97.78,99.36,99.0 9 ,9 8 .9 7 ,9 9 .0 4 ,9 7 .5 0 , 96.61 and 98.63 percent of the total variation in LSIV (Y) is already being explained by X variables of slope, relief, drainage, constant of channel maintenance, road contributing area, upslope contributing area, topographic index and land use and a considerable percentages (2.22,0.64, 0.91,1.03, 3.03,0.96, 2.50, 3.39 and 1.37) of variations in Y are yet to be explained. On an average 98.21% of Y variable is being explained by the corresponding X one. So, the result of R square shows that the independent variables of X (factors) taken here is giving a good explanation of Y (LSIV) variables.
Keywords
Landslide, Landslide Potentiality Index Value (LPIV), Landslide Susceptibility Index Value (LSIV), Landslide Zonation, Co-Efficient of Determination (R).- Shear Stress for Sediment Entrainment in connection with Grain Size at Lower Reach of the Rupnarayan River, West Bengal, India
Authors
1 Head of Department of Geography and Environment Management, Vidyasagar University, Midnapur-721102, West Bengal, IN
Source
Indian Science Cruiser, Vol 28, No 1 (2014), Pagination: 16-26Abstract
The lower reach of the Rupnarayan Rjver has experierced a net shoaling of 26.57 million with 42.04 million m3 deposition and 15.47 million m3 scouring during the last 20 years. Attempts have been made to calculate the available shear stress and critical shear stress in connection with the grain size of sediments.
Keywords
Shoaling and Scouring, Shear Stress, Sediment Texture, Skewness, Suspension.- Gully Erosion Control: Lateritic Soil Region of West Bengal
Authors
1 Department of Geography and Environment Management, Vidyasagar University, Medinipur -721102, IN
Source
Indian Science Cruiser, Vol 28, No 3 (2014), Pagination: 54-61Abstract
Gully erosion management on lateritic soil is a critical issue in West Bengal. In this paper, a combination with vegetation and check dams, for all aspects of lateritic soil erosion management has been discussed. A program for controlling gully erosion was carried out in Rangamati in lateritic soil region of western part of West Bengal from 2011 to 2012 that includes two approaches “Check dam” and “Vegetation cover”. Results indicated that at the initial stage, the percent of sand was the maximum in the upper catchment of each gully basin and the concentration of silt and clay was the least. Gradually as vegetation started trapping, the sediment composition of soil changed registering higher percentage of finer particles. Again, the nutrients detached from the upper catchment were arrested by check dams that induced nutrients supply and water storage, which in turn, increased the growth of vegetation. This proved the significance of vegetation cover with check dams to curb soil erosion. The results obtained may help the planners and managers to take proper decision for the conservation of lateritic soil.