Cyclone and Storm Surge - Iczmpwb.org

6.42
The above recommendations of the total 55 kms of retired embankment shall require land acquisition
of around 1947 hectare costing approximately Rs. 23 Crores as per 1997 price index. Though some
of the acquisition has already been done by now, but considering a gradual rise in land prices, the
cost of acquisition of the remaining land is about Rs. 30 Crore. Construction of these embankments
would require another Rs. 10 Crore.
6.3. Riverbank protection
This is the hard option of protecting a riverbank from failing under erosion. It is seen that the most
critical length of the rivers that need to be protected from failure by bank erosion is the 55 kms
identified in section 8.2 for retirement of the existing embankments. The bank protection has to be
done in a scientific manner, and using local material as much as possible. However, it is felt that hard
protections may be avoided since it may so happen that the protected bank remains safe under the
protection but the other banks which are unprotected start loosing a greater amount of material as a
result. Also the cost would be rather high. Instead, the region that is available as a result of retiring of
embankment may be planted with mangrove saplings as mentioned in the following section.
6.4. Mangrove regeneration
Mangroves have been known to help the coastal belts from the ravaging action of waves as
generated by tsunamis or cyclones. As is well known, and recorded by Sanyal (2006), when Tsunami
struck the Tamil Nadu during December 2004, the areas behind Pichavaram and Muthupet with
dense mangroves suffered fewer human casualties and less damage compared to areas without
mangroves. During October 1999, mangrove forests reduced the impact of a super cyclone that
struck Orissa killing at least 10,000 people and making 7.5 million homeless. The human settlements
behind mangroves did not suffer loss. During the year 1988 the devastating cyclone of Sundarban
damaged most of the embankments. But after the cyclone it was noticed that the embankments that
had either toe line mangrove plantations or natural mangrove buffer had hardly been damaged. The
most stable portions were the embankments where a ring dyke was also constructed and mangrove
regenerated in between them as in the Shikarpur forest campus and its vicinity.
Mangroves are efficient silt trappers and it has been proved that the delta progradation of Sundarban
largely depend on the sediment trapping by the mangroves. The presence of mangroves at the
intertidal flats on foreshore of the embankments also helps in sediment accretion at the base of the
embankments and strengthening it in turn. The dearth of sand in the old Digha sea beach is partially
related to the mangrove clearance of Digha Mohana estuary for a large scale co-operative Fishery