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Cyclone and Storm Surge - Iczmpwb.org

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2.9<br />

(aligned perpendicular to the shoreline) separated by intervening swales e.g. Jambudwip <strong>and</strong><br />

Chuksardwip.<br />

• Mesotidal (tidal range: 2—4m) Midnapore (Digha—Junput) coastal plain to west of the<br />

Hooghly estuary. Successive rows of dunes with intervening clayey tidal flats are<br />

characteristically present in the coastal plain.<br />

The “Ancient dune complex” all along the Midnapore coastal plain (about 10 to 15 km north of the<br />

present shoreline) indicates the position of the “Ancient str<strong>and</strong> line” in the area. The C 14 dating of<br />

sediments from “Ancient fluvio-tidal flat” (5760±140 YBP) present in the north of the “Ancient dune<br />

complex” confirms that the higher str<strong>and</strong> line in the post-glacial (Holocene) period is at present<br />

represented by the “Ancient dune complex” which is around 6000 YBP – the optimum of the<br />

Fl<strong>and</strong>rian transgression (Selby, 1985). The C 14 dating of sediments from “Ancient intertidal flat” (just<br />

south of the “Ancient dune complex”) gives an age of 2920±160 YBP which indicates the first<br />

punctuation in the regression of the Holocene sea in the area under consideration.<br />

The “Ancient dune complex” does not extend in the eastern part of the Hooghly river. Careful<br />

analysis of the satellite imagery reveals the presence of a morpho-structural lineament in the same<br />

alignment as that of the aforesaid dune belt <strong>and</strong> passes just north of Sagar Isl<strong>and</strong>, through Kakdwip,<br />

in a north-easterly direction towards Bangladesh separating the lower deltaic plain of Ganga-<br />

Brahmaputra (within India) into two sectors, as mentioned below:<br />

The areas to the south of this line are characterised by the presence of isl<strong>and</strong>s (draped with<br />

mangroves) separated by an network of active tidal creeks,<br />

The areas to the north of this line are almost free from such network embroidery of tidal creeks <strong>and</strong><br />

isl<strong>and</strong>s. The Sundarban falls in the first group occupying the area south of the lineament. In Hooghly<br />

estuary, in the south of this morpho-structural lineament, the sticky grey clay of inter-distributary<br />

mangrove marsh unit (equivalent to the “Ancient intertidal flat” unit of Midnapore coastal plain) is<br />

characterised by the brackish water mangrove bio-assemblages (for example Ceriops, Rhizophora,<br />

Chenopodiaceae, Heriteria, Gramine (Poaceae), Palmae (Aricaceae), Circulisporites etc.). The C14<br />

dating of this clay sample from Namkhana giving an age of 3170±70 YBP <strong>and</strong> 2900±20 YBP from<br />

Gangasagar indicates the progressive southward shifting of coastline towards the present shoreline<br />

in recent past.<br />

We briefly discuss each of these coastal zones <strong>and</strong> the vulnerability due to cyclonic hazards in the<br />

following sections.

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