Coastal erosion in response to wave dynamics operative in Sagar Island, Sundarban delta, India |
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| Authors: | Barendra Purkait |
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| Institution: | (1) Geological Survey of India, Map and Publication Division, 29, J. L. Nehru Road, Kolkata, 700016, India |
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| Abstract: | Coastal erosion at Sagar Island of Sunderban delta, India, has been critically studied. The area is in the subtropical humid
region. There are mainly three seasons viz: winter, summer and the monsoon. Different wave dynamic parameters were measured
from theodolite observations with leveling staff and measuring gauges during lunar days at two sections of the western and
eastern parts of the coastal zone during post-and pre-monsoons. A comparative study was made on the erosion/depositional pattern
between the two sections in relation to different hydrodynamic parameters prevailing in these two sections. Plane table mapping
was carried out to demarcate the different geomorphic units. The marine coastal landforms show dune ridges with intervening
flats bordered by gently sloping beach on one side and a flat beach on the other side. The western part of the beach is mainly
sandy; whereas the eastern part is silty and clayey with mud bank remnants. Actual field measurements indicate that the coastal
dune belt has retreated to the order by about 20 m since 1985. The eastern part of the beach has lowered by about 2 m since
1985 and the western part was raised almost to the same tune. It is observed that accretion in the western and central parts
of the beach took place; whereas severe erosion in the eastern part made the beach very narrow with remnants of mud banks
and tree roots. Frequent embankment failures, submergence and flooding, beach erosion and siltation at jetties and navigational
channels, cyclones and storm surges made this area increasingly vulnerable. |
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| Keywords: | Bay of Bengal coastal erosion Sagar Island Sundarban delta wave dynamics |
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