Cyclone and Storm Surge - Iczmpwb.org
Cyclone and Storm Surge - Iczmpwb.org Cyclone and Storm Surge - Iczmpwb.org
6.47 15. Ceriops tagal 0.22 0.40 0.50 0.61 1.72 16. Phoenix paludosa 0.40 0.55 0.70 0.85 1.05 17. Nypa fruiticans 0.50 0.60 0.76 0.95 1.20 6.5. Coastal erosion protection The total length of coastal embankment in West Bengal is about 58 kms stretching from the Orissa- West Bengal border west of Digha upto the Rasulpur river. It is maintained by the Irrigation and Waterways Department, Government of West Bengal. The embankment protects the inundation of inland habitated areas from the wrath of violent cyclonic storms and consequent storm surges. However, the embankment is not very close to the sea at all places. At Chandpur, for instance, it is so close to the sea that it has been eroded off along a considerable length. At places like Shankarpur, the embankment is safe, but a large chunk of coastal shelter belt plantation of Casurina trees have come under the threat of erosion by the dashing sea waves. The jetty at the same place has been washed off, and at present some temporary measures have been taken by the Irrigation and Waterways Department, to reduce the effect of the waves. At Digha, the erosion of sea beach has been prevented from further recession by providing a very costly revetment using concrete blocks. But just east of this section, there is severe erosion and a big patch of Casurina shelter belt plantation is presently under threat of being wiped away. It may be noted that in the past couple of decades, quite a good area of such plantation has already been devoured by the sea by repeated wave action and enhanced wave dashes during cyclonic storms. As such, the severely affected portion of the coastal embankment that is affected by erosion (and enhanced during occurrences of cyclones) is estimated to be about 20 kms. This is because not all coastline of West Bengal is affected by erosion. In fact, at Junput, there has been a lot of deposition and the shoreline has shifted seawards over the years. Anyway, the reach that is affected by severe erosion needs immediate attention, otherwise valuable land is likely to get lost due to shoreline recession and consequent loss of human habitated land areas. A possible solution to counter the sea face erosion is to provide a boulder revetment underlain with geotextile, as shown in Figure 6-20. This design has been taken from the Manual on the use of Rock in Hydraulic Engineering published by the Road and Hydraulic Engineering Division of the Government of Netherlands. It has been tested in many locations along sea faces, though certain other methods may also prove equally useful.
6.48 Figure 6 -20. Typical coastal revetment sections The cost of providing this kind of protection would cost nearly 4 Crores per km. Thus, for the protection of the severely affected sea face of 20 kms as identified in the above paragraphs, an amount of Rs. 80 Crores is required to be invested. 6.6. Shelterbelt plantation To protect the settlements along the coast line, especially along the coast of East Midnapore district, shelterbelt can be provided as wind break. Species like Casurina, Subabul etc which are locally available serves the purpose effectively. The plantation width and orientation should be guided by the wind direction and the alignment of the human settlement. Care should be taken that the plantation is not monoculture but accommodates diverse range of species. Plantation of cash crops, especially coconut, palm etc will increase the biodiversity of the shelter belt plantation along with increasing community participation in maintaining them. It has been observed that the landfall of cyclone takes place for a reach of about 50 kms – out of which approximately 30 km stretch does not have either any kind of plantation or have depleted over time. The estimated expenditure for plantation of
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6.48<br />
Figure 6 -20. Typical coastal revetment sections<br />
The cost of providing this kind of protection would cost nearly 4 Crores per km. Thus, for the<br />
protection of the severely affected sea face of 20 kms as identified in the above paragraphs, an<br />
amount of Rs. 80 Crores is required to be invested.<br />
6.6. Shelterbelt plantation<br />
To protect the settlements along the coast line, especially along the coast of East Midnapore district,<br />
shelterbelt can be provided as wind break. Species like Casurina, Subabul etc which are locally<br />
available serves the purpose effectively. The plantation width <strong>and</strong> orientation should be guided by the<br />
wind direction <strong>and</strong> the alignment of the human settlement. Care should be taken that the plantation<br />
is not monoculture but accommodates diverse range of species. Plantation of cash crops, especially<br />
coconut, palm etc will increase the biodiversity of the shelter belt plantation along with increasing<br />
community participation in maintaining them. It has been observed that the l<strong>and</strong>fall of cyclone takes<br />
place for a reach of about 50 kms – out of which approximately 30 km stretch does not have either<br />
any kind of plantation or have depleted over time. The estimated expenditure for plantation of
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