Nearly five months after the December 26 tsunami calamity, the Navy is shifting its focus from relief works to one of its most formidable tasks — remapping the entire Bay of Bengal over a period of 12 months.With navigational points, marine structures and coastal oceanic depths thrown into disarray by the oceanic upheaval on the Andaman & Nicobar Islands in December, the Naval Hydrographic Department (NHD) will now engage in a laborious exercise to re-draw 94 navigational charts for the islands and the mainland’s Eastern seaboard.In an exclusive preview to The Indian Express of what lies ahead, NHD’s Chief Hydrographer Rear Admiral B.R. Rao said, ‘‘Fantastic changes have taken place, the water ingress has been tremendous on the islands. Depths have changed. It is a long process ahead. The data has to be absolutely fool-proof. We will be completely re-drawing 45 navigational maps on the East Coast and 49 maps on the islands alone.’’Fundamentally, while there has been no rise in ocean levels at the islands, the new coastal depths have been caused by the islands themselves being jolted either up or down by the Indian tectonic plate slipping partially under the Burma plate. To the untrained eye, the depth changes may seem trivial — the water is deeper by a metre on average at Port Blair’s coast and 1.5 metres at Campbell Bay — but these translate into comprehensive considerations for mariners docking at the islands.That’s not all. Consider this: all navigational aids on the islands have been destroyed and only some repaired. The navigational points at Camorta Island, Campbell Bay, Diglipur, Mayabander and Rangat Bay also stand altered because of changes in water level, ranging from 0.3 metres to 1.5 metres.As an interim measure, the Navy continues to issue notices to mariners on the altered depths so they are forewarned even of minor changes at all harbours on the islands. Rao presents the example of Diglipur, where estuaries have gone dry, coral reefs have come up and mud flats have emerged, substantially shallowing the water. The jetties of Nancowry, Hut Bay and Tarasa Bay are all now out at sea.Rao’s team has also observed widespread creation of new shoals, migration of existing shoals, drastic changes in the shoreline and topography and a dislocation of navigational marks. And some beaching points like Trinkat island, Chowra, Bompoka and Katchall may have to be deleted from the new maps, because they no longer have beaches. But Rao, with eight blue-water capable ships at his disposal, has his plan sorted out. ‘‘Hydrographic instructions have been issued to harbours that have been severely affected. Near the coast, there are still substantial changes, but navigation out at sea is still not so much of a concern since the depths there are far greater,’’ Rao said. To begin with, the NHD will re-survey and draw the charts for Port Blair (Map Code 4001), Campbell Bay (4035), Diglipur (4003), Rangat Bay (4006), Maya Bandar (4008) and Nancowry (4005).The strategic importance of the islands has been recognised far more since the tsunami — it is the critical turn-around and servicing points as warships venture into bluer waters further south. The shipping channel blends into one of the busiest lanes in the world. And Rao does not miss the irony of his task. Just a year ago, the Navy had completed a brand new set of charts for the islands. Now, with check surveys complete, his team will wait till the monsoon recedes before getting to work. On calmer water.
