Exploring drainage/relief-scape sub-units in Atreyee river basin of India and Bangladesh

Swades Pal,Tamal Kanti Saha 대한공간정보학회 2017 Spatial Information Research Vol.25 No.5

The prime objective of this study is to identify drainage and relief diversity models of the Atreyee river basin of India and Bangladesh for showing some relief and drainage sub units with unique characters. To achieve the goals, 20 associated morphometric parameters (e.g. drainage density, drainage frequency, relative relief, ruggedness number, slope, hydraulic gradient, dissection index etc.) have been used as spatial raster data layers. Weighted compositing method is applied for computing these models. Diversity models are classified for achieving the subcategories of the relief and drainage and each sub category possesses homogenous morphometric features. The high drainage diversity is found in the northern and middle western part especially along the Atreyee river and few patches of the alluvial tract. Although out of the total area only 8.98% area (1982.03 km2) falls under the very high diversity zone and in this area drainage density, frequency, texture etc. are also high. The high relief diversity zone (1.54%) displayed at the source and some middle western part of the basin. These models are also validated using some individual parameters using spatial correlation methods. High correlations significant at 95–99% level satisfy the sensitivity of Drainage and Relief diversity models.

Impact of flood and seasonality on wetland changing trends in the Diara region of West Bengal, India

Kaustuv Mukherjee,Swades Pal,Malay Mukhopadhyay 대한공간정보학회 2018 Spatial Information Research Vol.26 No.4

The hydrological condition of any floodplain wetland depends on the water availability through surface run-off from adjacent areas. The seasonal variation of rainfall and resultant flood bring massive change in the wetlands of that region. The present study focuses on identifying wetland inventories and trend of wetlands of the Diara region of West Bengal. Diara region of Eastern India is a highly dynamic physical region bounded by two frequently shifting rivers (River Ganga and Kalindri) and relatively tightly bound river Mahananda in its three sides. Two types of Normalised Difference Water Index, water presence frequency and hydrological stability analysis using LANDSAT data of 1973–2016 have been done for this study. The result shows that the wetland area was 14,124.78 ha during 1999 and it has turned into 4885.92 ha during 2016 which indicates the extreme flood event of 1998–1999 over entire region has brought a boost in the wetland scenario for a shorter period but it is in the decaying phase now-a-days. Total 1552.56 ha of wetland in this area is identified as stable based on the regular appearance of water over there.

Application of numerical models to simulate the charland area from Rajmahal to Farakka barrage of the Ganga river of eastern India

Rajsekhar Chakraborty,Swades Pal 대한공간정보학회 2020 Spatial Information Research Vol.28 No.6

The present work intends to predict char area in river Ganga from Rajmahal to Farakka barrage using advance machine learning models for justifying the sustainable habitability of the charland. Artificial neural network (ANN), end point rate and linear regression for spatial and ANN, radial basis function, random forest, support vector machine (SVM) models for numerical charland prediction are used. Historical charland study since 1990 to 2018 exhibits 34.32% increase 46.86% decrease of total charland and river flow areas respectively. Amongst the spatial prediction models ANN has effective predictability with acceptable performance level. In coming 20 years no significant change will happen in case of Bhutni and Piarpur charland. Amongst the numerical models by 2038 charland area is likely to be expanded as predicted by ANN and SVM models with statistical significance. Based on the findings it can be recommended that for predicting dynamic charland area ANN model could be used both at spatial and numerical scales. The findings also exhibits that charland area is expected to be enhanced and it has immense planning importance specially for finding habitability in charlands.

Estimating wetland insecurity index for Chatra wetland adjacent English Bazar Municipality of West Bengal

Sk. Ziaul,Swades Pal 대한공간정보학회 2017 Spatial Information Research Vol.25 No.6

Charta wetland adjacent to the English Bazar Municipality is considered as the kidney of this urban area. In last 25 years, 43% of total wetland area is urbanized and this trend still continues. This paper aims to compute wetland insecurity index based on 11 selected natural (five) and man induced parameters (six) at multi-temporal scale (1990, 2010 and 2017). Weighted linear combination method is used for preparing wetland insecurity indices (natural, man-induced and integrated parameters specific) in Arc GIS (v-9.3) environment. Result clearly exhibited that man-induced parameters are more crucial for bringing greater north eastern wetland fringe area under high insecurity. Highly insecure wetland covers 6.6% to total area in case of man-induced parameters based spatial model is recorded in 2017 superseded previous phases. In case of natural parameter centric wetland insecurity model, no such highly insecure zone is found. Total 20.17, 33.23 and 72.18 ha areas are appeared as highly insecure wetland area for integrated wetland insecurity models for 1990, 2010 and 2017 respectively indicating increasing spatial extent. Built up area, population density, sedimentation seasonal drying out of the parts of wetland are appeared as major reason behind growing wetland insecurity in Chatra wetland.

Exploring landslide susceptible zones by analytic hierarchy process (AHP) for the Gish River Basin, West Bengal, India

Tirthankar Basu,Swades Pal 대한공간정보학회 2017 Spatial Information Research Vol.25 No.5

Landslide is a major threat in the Darjeeling Himalaya within sub-humid climate. Hence proper identification of landslide susceptible zone (LSZ) is very much essential. In this case a multi criterion evaluation approach is applied using thirteen selected indicators. The parameters are categorized into five categories viz. anthropogenic factor, surface causal factor, lithological causal factor, triggering factor and protective factor. Weighted composite model is prepared adopting weighting base as Analytic Hierarchy Process. The obtained result shows that near about 19.92 sq. km (approximately 7.52%) area within the basin is highly susceptible for landslides. High drainage density (avg. 4.31 km/sq. km), relatively steeper slope ([10) accelerate this process. Beside the main landslide susceptibility layers five separate models of five causal factor groups are prepared and correlated with final LSZ for understanding the priority cluster. Lithological factors cluster appears as a dominant factor group (correlation value 0.95). This LSZ model is also validated by frequency as well as areal density of historical landslides. Beside this, the validation by ROC curve shows 84.00% area under the curve. So, the model can be treated as relevant.

Exploring geospatial changes of wetland in different hydrological paradigms using water presence frequency approach in Barind Tract of West Bengal

Rajib Tarani Das,Swades Pal 대한공간정보학회 2017 Spatial Information Research Vol.25 No.3

The Barind tract of West Bengal is composed with old alluvial soil, relatively undulating plain with good number of riparian wetlands. The main source of water of these wetlands is rain water and inundated water from river because most of the natural wetlands are located alongside the river. Under this condition any kind of river flow modification may influence the present wetlands condition. A good number of dam/reservoirs have been constructed on river Atreyee, Punarbhaba, Tangon etc. and it causes flow modification in those rivers in their downstream. The main objective of this paper is to find out the consequence of such river flow modification on areal extent of wetland, seasonal dynamics of wetland, temporal trend and their vulnerability. For doing this work Landsat image of premonsoon and post-monsoon season since 1988–2016 have been collected from USGS website. After that water presence frequency approach is used for wetland mapping and detecting change in pre and post dam regime. From the analysis it is found that in post dam condition both quantitative and qualitative degradation are being happened and their rate varies in different interfluves zones. It is also found that the degree of vulnerability has been increased in post dam condition. Considering the ecological values and their capability of livelihood support scientific delineation of wetland boundary according to their degree of vulnerability is essential.

Exploring the ambient environment for charland formation in Rajmahal downstream Ganga river of Eastern India in post Farakka barrage Period

Shahana Khatun,Somen Das,Swades Pal 대한공간정보학회 2018 Spatial Information Research Vol.26 No.3

Up to 2005, more than 700,000 people and 53 villages of Malda and Murshidabad districts have been displaced and wiped out due to bank erosion of river Ganga. Population displacement due to massive river bank erosion and rehabilitation for them with livelihood options are the emerging challenge in both up and downstream of Farakka barrage. This paper also wants to find out potential areas of charland formation along with exploring existing charland over the selected phases. Normalized differences water index (NDWI) from 55 Landsat images is used for flow and charland mapping. Water presence frequency (WPF) and NDWI map are taken as parameters for mapping new habitat for chaland. Total existing charland area in phase 3 is 463.58 km2 and potential habitat for charland is 117.59 km2. Out of this potential area, in post monsoon season, 35.26% comes under highly potential zone where both depth of flow is very low and frequency of flow is irregular. Highly suitable area has been increased over the recent phases. Potential charland maps in 1st and 2nd phases are validated in reference to the appeared charland area in the successive phases. New charlands expectedly would be the resource hunting ground of the displaced people.

Habitat identity crisis caused by the riparian wetland squeeze in Tangon River Basin, Barind Region, India

Rajsekhar Chakraborty,Swapan Talukdar,Tithankar Basu,Swades Pal 대한공간정보학회 2018 Spatial Information Research Vol.26 No.5

The present paper intends to delineate flood plain wetland in Tangon river basin (1988–2016) from Landsat images and to investigate the nature and causes behind squeezing wetland and losses. From the analysis it is found that the total recognized average wetland area in pre monsoon season and post monsoon season are respectively 13.37 and 67.05 km2 in post dam period whereas in pre dam period it was 12.75 and 77.78 km2 respectively. Flow reduction due to damming over Tangon in 1989 is one of the major causes behind squeezing wetland area. Agriculture extension replacing shallow and seasonal wetland, disconnection of discharge contributing Karatoya river form Tangon river, gradual disconnection with ground water column are the crucial reasons for growing wetland habitat quality. Inconsistent water supply, frequent drying up of wetland fringe area withstand against health of the wetland habitat. Considering the causes of habitat crisis, immediately agricultural extension reclaiming wetland should be stopped, ecological flow should be allowed from dam. These steps could minimize the growing habitat crisis in the study region.