Watch out, Vembanad estuary is shrinking

ach year, Vembanad estuary is shrinking by 0.288 sq km, which would leave serious ecological impact on the lives on its banks.

A group of researchers from the National Institute of Oceanography, Goa, came to the conclusion after evaluating the coastal morphological data of 44 years between 1967 and 2011.

The research team consisting of P.K. Dinesh Kumar, Girish Gopinath, R. Mani Murali and K.R. Muraleedharan noted that the “rapid pace in urbanisation in the region has brought tremendous changes to the major islands in the estuary.”

The erosion and accretion of the estuary was studied by comparing satellite imageries of 2004 and 2011 with the topo-sheet of 1967 of the Survey of India. The results conclusively showed that the estuary was being inflicted with major geomorphic changes at several segments, resulting in reduction in its extent, it said.

The “narrowing and squeezing of the estuary” was observed at several segments. This was posing a “significant threat to estuarine habitats and functions.” The Geo-morphologic differences found in the land-water system may lead to modification of estuarine flows. The bulging of islands due to sedimentation and the presence of new islands will reduce or alter the estuarine flows, a research paper published by the scientists said.

During the period of 1967- 2004, major shoreline changes had taken place in the northern segments of the estuary mouth, where as the southern zones exhibited only minor variations in the widths.

Over the four decades, major changes in land area were seen in Vallarpadaom Island, Willington Island, and Vypeen Island, whereas islands such as Perumbalam, Kumbalam, Nettur, Madavana, Arukutti, Thaikkatusseri, Cheppanum, and Chottammel in the estuary exhibited minor changes during this period, they concluded.

The accretion in the major barrier island of Vypeen Island resulted in the shifting of the shoreline in the seaward direction.

During 2004 -11, the shoreline position in Vypeen Island moved slightly to the east, resulting in the erosion of about 0.278 sq km of land area. During the period 1967- 2011, the shoreline to the south of estuarine mouth also moved gradually eastward. Comparative analysis of satellite imageries available for the region for 2004 and 2011 showed a marginal decline in the area of Vypeen Island by about 0.278 sq km landward. In 2004, tsunami waves hit these shores, which might have resulted in this change, the paper concluded.

The bulging of islands due to sedimentation and the presence of new islands will reduce or alter the estuarine flows