275 sq km land lost at Rohmoria, Dhola
Prabal Kr Das
GUWAHATI, June 7 – It is a wake up call for policy framers to have a fresh look at erosion caused by the Brahmaputra. A study has now sharpened focus on the severity of bank-line and channel migration of the river between Rohmoria and Dhola in upper Assam.
The study reveals that a total of 275 sq km of land has been lost to erosion during 41 years, of which 57.9 sq km was eroded between 2000 and 2006 alone, and another 14 sq km of land disappeared between 2006 and 2008.
The study conducted by a team from the Geological Sciences Department of Gauhati University indicates that around 6.8 sq km of valuable land on average was lost to the river every year.
Analysing data, a large part of which included satellite imagery, the team using the Quaternary Geology and Geomorphology Lab were able to identify the areas where the Brahmaputra has caused the maximum damage. In an area east of Rohmoria, the river has widened to an astonishing 19.7 km.
According to Parag Phukan, who initiated the study, findings prove that rapid erosion is taking place in the south bank, while major depositions have been scarce.
The erosion has not only caused reduction in land available for settlement, cultivation and plantation, it has also adversely affected the Dibru Saikhowa National Park. The study found that from the size of 281.90 sq km in 2000, the protected area has been reduced to 254 sq km in 2008.
Phukan pointed out that activation of a new channel south of Dibru Saikhowa has been responsible for destruction of sizeable land resource. It was found that 459.3 sq km was affected by avulsion of the channel.
Satellite images compared to ground based data have shown that between 1967 and 2000, around 160.5 sq km of land was eroded around the Dibru Saikhowa area. There were depositions, but that amounted to a mere 41 sq km.
When asked about the quality of the database, Phukan said that the earliest source was the 1967 topomap, and the last was imagery from IRS P6, which provided a resolution of 23.5 metres. He expects to use the latest high resolution satellite imagery soon, which would provide more detailed information about the erosion caused by the river this year. Source: Assam tribune