Sutapa Mukhopadhyay

Quantitative study on shoreline changes and Erosion Hazard assessment: case study in Muriganga–Saptamukhi interfluve, Sundarban, India

Quantitative techniques, statistical methods and mathematical rules make the geospatial analysis more systematic, accurate and precise. In order to measure the intensity of the ongoing processes on the earth surface, evaluate the spatio—temporal changes in geographical attributes, highlight the principal factors for any geographic events and to identify the future possibilities, quantitative techniques are for most dependable. In the present article sequential changes of the shoreline, spatio—temporal extent of erosion and depositional processes of Sundarban region, West Bengal, India, have been measured following the selected quantitative techniques. The Sundarban is one of the most dynamic geomorphic units in the earth surface, situated in the northern apex of Bay of Bengal. The region has formed, sculptured and modified due to continuous sedimentation of the Ganga and the Brahmaputra systems, intense tidal hydro dynamic behavior, climatic disturbances and anthropogenic activities. In the last two century most of the parts of the active Sundarban delta has being reclaimed and occupied with dense rural settlements, most of the peoples are engaged in agriculture based rural economy, hence substantial erosion and successive regressive changes in the area have an unconstructive impact on the dwelling communities. In order to examine the net shoreline changes, average rate of end point changes and extent of erosion and depositional processes Survey of India toposheets of 1920, 1921, 1922, 1923, US Army toposheets of 1955, Survey of India toposheets of 1967, 1968, 1969 and IRS P6 LISS IV satellite images of 2014 have been used. Finally erosion hazard zones have been identified will help of net area changes of the each geomorphic units to access the spatial variation of erosion hazard intensity. Quantitative model has been prepared on the basis of multi temporal data of Muriganga–Saptamukhi interfluve area of western Sundarban which can be applied to the other parts of Sundarban region.

An assessment on the nature of channel migration of River Diana of the sub-Himalayan West Bengal using field and GIS techniques

Lateral movement of river channel within its valley with time is a universal phenomenon. Various processes of fluvio-geomorphological environment such as rapid valley fill deposition due to very low channel gradient and resultant migration of active channel, bank failure and bankline migration, frequent occurrence of floods, capturing of lower courses of the tributaries by the trunk streams, and abandonment of tracks and avulsion are the most prominent factors behind channel dynamics in the sub-Himalayan part of West Bengal. Additionally, human interventions in the form of engineering constructions (bridges, flood embankments, etc.), tea plantation, mining and quarrying, and agricultural encroachment have emerged as another dominant issue which is pulverizing the ways of natural channel adjustment as well as also the channel behaviors. Both these processes are carrying significant messages of immense vulnerability for the study area known for its geomorphological instabilities. The dynamics of channel adjustment in terms of lateral migration can be lucidly illustrated through the application of modern tools of geoinformatics, i.e., the techniques of remote sensing and geographic information system (GIS) which is widely capable of detecting as well as representing the changes that took place over space and time. A meticulous endeavor has been made to assess the channel dynamics of the Diana River of this concerned region for an 85-year spanning period to unveil the nature of channel migration in terms of changes in historical bankline and centerline positions and alterations in meander geometries through numeric and graphical methods coupled with field observations to define the overall zone of channel migration for three subsequent reaches of the Diana River.

Correction to: Vulnerability assessment through index modeling: a case study in Muriganga–Saptamukhi estuarine interfluve, Sundarban, India

In the initial online publication of this article the functional relationship between vulnerability and recovery day has been typed as “inverse” in the Table 1 column four and row thirteen which should be replaced as “direct” because more recovery day shows lack of proper adaptive capacity and therefore it is positively related with misery and sufferings and vice – versa.

Vulnerability assessment through index modeling: a case study in Muriganga???Saptamukhi estuarine interfluve, Sundarban, India

The coastal regions, deltas, and estuaries are severely affected by the sea level rise and cyclonic activities and climate changes. Sundarban delta is one of the most mysterious landscapes in the world, which has successively evolved due to sediment accumulation by the great Ganga and Brahmaputra river system. The area is characterized by low-lying islands and a flat topography coupled with macro-tidal activities, powerful surges, and seasonal cyclonic events. All these conditions put together this landscape defenseless to frequent flood and erosion. Since the last hundred years, the face of Sundarban has been changed remarkably from wildest to human-occupied territory by protecting this low-lying flat plain from tidal inundation through artificial embankment. In this background, the current study attempts to highlight the spatial extent and magnitudes of internal risk factors of the region using the composite vulnerability index. Coastal vulnerability defines a system’s openness to flood and erosion risk due to hydrogeomorphic exposures and socio-economic susceptibility in conjunction with its capacity/incapacity to be resilient and to cope, recover, or adapt to an extent. Coastal vulnerability assesses the potential risk from erosion and flooding of any low-lying coastal region due to its physiographical and hydrological exposures, socio-economic and political susceptibility, and resilience capacity. A natural system affects the socio-economic scenario of any region. Hence, multidimensional databases can be more effective to understand the extent of exposure, susceptibility, and resilience of any system. To throw some light on the situation of vulnerability of western estuarine Sundarban, between Muriganga and Saptamukhi interfluve, the composite vulnerability index has been carried out to delineate the magnitude and spatial extent of vulnerability with the help of quantitative techniques and geospatial tools. The estuarine tracts and coastal parts of the Ganga delta are two of the most densely populated areas in the world. The study highlights the critical situation of the population under different potential risk classes residing in the study area with the intention of suggesting some proper course of action of planning and management to conserve coastal communities in their original habitat.