Cuttack, September 11 (odisha.in) A wild life body Tuesday demanded a study on the sea erosion at coastal town of Puri that threatened to swallow the hotels and buildings located close to the beach road.
Geologists and oceanographers are puzzled over the recent sea erosion noticed at the beaches of Puri town. The beach has never faced this kind of erosion before and this is surprising since the beach profile has been quite stable since the last 100-200 years, secretary wild life society of Orissa Biswajit Mohanty said.
Beach erosion noticed along the Orissa coastline is seasonal and most of the beaches manage to regain their original shapes over an annual cycle by March/April.
However, it is also noticed that some beaches undergo net erosion and at least 50 per cent of the beaches do not regain their original profile. Orissa has a total coastline of 476 kms out of which sandy beaches account for 57 per cent of the coastline.
In a recent letter to the Chief Minister, the Wildlife Society of Orissa has pointed out the need for detailed studies to establish the impact of the Chilika new mouth on beach erosion at Chilika.
The Society has pointed out that the unprecedented erosion at Puri could be correlated with the opening of the new mouth at Chilika lake done on 23rd September, 2000. Coincidentally, beach erosion at Puri is noticed since the last 4-5 years, he said.
There are doubts whether the proposed sea wall construction at Puri could solve the problem since it would lead to the loss of a very popular beach as well lead to huge costs in maintenance.
Along the east coast of India, long shore sediment transport is southerly from November to February, northerly from April to September and variable in March and October.
According to a scientific paper “Coastal process along the Indian coastline” published by four scientists of National Institute of Oceanography in August, 2006, it is observed that the annual net longshore sediment transport rate (LSTR) of 9, 40,000 cubic metres /yr at Gopalpur, Orissa was northerly, which is similar to that observed between Prayagi and Puri .
The gross LSTR is about 10, 00,000 cubic metres / yr along south Orissa.
Measurements conducted by scientists prior to the opening of the new mouth show that the net LSTR at Gopalpur and Prayagi both of which are south of Chilika is 830,046 cum/year and 887,528 cum/year.
However, at Puri, the net LSTR figure drops to 735,436 cum/year which clearly indicates that the currents arrive at Puri only after depositing a part of their load south of the town.
Though the currents picked up sediments from the Puri coast to make up for the loss, this beach could recover its original profile after the monsoons when the currents turned north to south and deposited a part of the sediments they had picked up earlier.
Currents have a predictable behaviour of picking up sediments from their paths, if they are forced to deposit their sediment load due to disturbed flow caused by man made obstructions like ports and coastal structures.
Prima facie evidence is now available that the rate of deposition has increased after the Chilika new mouth was opened since massive movement of littoral sediments has lead to the formation of long sand spits and sand banks near the new mouth during the last 4-5 years. The Chilika new mouth is only 36 kms away from Puri town, he said.
This delicate equilibrium which was maintained earlier is now disturbed due to the new mouth at Chilika where tidal flux forces the currents to deposit a part of their load near the mouth before reaching Puri beach.
During high tide when sea water gushes into the lake, the sediments are deposited inside the lake in front of Sipakuda village. Similarly during low tide when the waters recede, the deposits accrete in front of the new mouth inside the sea.
However, only expert studies using advance mathematical models can confirm the extent of impact of the Chilika new mouth on the erosion process seen at Puri beach. Once findings are available, the only way to save Puri beach would be by mitigating the effects of the new mouth through dredging and sand nourishment or through building breakwaters.
Earlier studies by National Institute of Ocean Technology (NIOT) had revealed the progressive loss of beaches in the Gahirmatha Marine Sanctuary over the last three decades which were attributed to the the establishment of Paradeep port in 1966 on the Orissa coast, south of the Mahanadi river mouth.
This case clearly illustrates the effects of disturbed current flow which could impact beaches situated 30-40 kms away, he said.