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Centre for Distributed Computing



A Secure Decentralized Disaster Management Information Network (SDDMIN) Using Rapidly Deployable Wireless Networking & Mobile Computing Technologies   

Micro-level multihazard risk zone mapping has been done using Toposheet, GPS and satellite images through direct field survey of Gosaba Block of South 24 Parganas, West Bengal. 

Major findings are as follows : 

1. Almost all the parts of Sundarban delta are multi-hazard natural disaster prone and are frequently attacked by storm surge, cyclone, tidal flood, embankment erosion, water logging due to basin shaped structure of the human habitated islands. The area is also within the map of earthquake zones.
2. The inner boundary of the nine (9) islands of Gosaba block is flowed by creeks originated from the rivers Bidya on the south-western part of the block and Raimangal on the north eastern part of the block.


3. Distributaries like Saptamukhi, Jamira (Thakuran), Matla and Bidya are beheaded by losing link channels to the Ganga and straightened their lower courses in search of a shorter route to the sea.
4. This was caused by a flexure in the basin floor, marked by the Calcutta -  Maymansingh hinge zone, due to eastward tilting and subduction of the Indian Plate below the Burmese Plate.
5. A major flow of sediments took place at the eastern part of the block replacing the old braided pattern, characteristics of the rivers at confluence, by a post Holocene meandering geometry. Now, the wide funnel shaped mouths are being attacked by seawaves and destructive tidal currents.
6. If uninterrupted, all the rivers and creeks overflow during high tides and the saline muddy water spreads over the adjoining flat lowlands. The silt settles down and raises the lands through this natural process. Through premature reclamation this process is interrupted by the construction of earth embankments all along the length of the channels. As a result, the silt arrested by the embankments on either side of the channel settles in the channel bed and raises it steadily which in consequence raises the water level, especially during high tide and increases the vulnerability factor of the embankments.
7. The wide funnel shaped mouths of the distributaries like Saptamukhi, Jamira (Thakuran), Matla, Bidya and Raimangal together mobilize sea water from about 60 Km across the Bay of Bengal. Marine water enter through various channels inside the islands of the block after traversing 40- 60 Km from the mouth of the rivers. The length of these inside channels varies from 2 Km to 100 meters encircling the islands of the block.



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