GUWAHATI: The problem of urban flooding will worsen so much in the future that people in certain areas of the city will be forced to leave. This doomsday warning has come from experts who have been for years studying the problem of rapid and haphazard urbanisation in the city.
In the last 20 years, rapid urbanisation has disturbed drainage channels and wetlands in the city, which has compounded the problem of urban flooding. To solve this, Abani Kumar Bhagawati, professor of geography at Gauhati University, sees no other alternative other than to revive the wetlands and drainage channels.
“There were no floods in the city until there were sufficient wetlands to soak up rainwater and channels to carry excess water to the Brahmaputra. Now, the natural topography has been destroyed by human interference,” Bhagawati added.
Detailing his findings over the years, he said the natural drainage system has faced severe human interference. “Encroachment and concretisation are the two primary reasons for floods. This has reduced the open areas to soak up water naturally. As a result, water flows into the existing channels that don’t have the capacity to carry such a huge volume of water. So, the city gets inundated with just half an hour of rain,” Bhagawati said.
The city has five broad drainage basins — Bharalu basin, Silsako Beel basin, Deepor Beel basin, Kalmoni basin and Foreshore basin. These have their own natural channels to carry excess water.
These include the Bharalu-Bahini river system, Mora Bharalu river, Basistha river, Lakhimijan channel, Bondajan channel and Khanajan river. All these river systems and channels eventually drain excess water into the Brahmaputra.
Bhagawati said the obstruction of the Bondajan channel is the latest and most serious example. “This happened in the last 20 years. The Narengi-Six Mile road has been constructed, disturbing the Bondajan channel area. Rainwater, finding no way to get to the channel, inundates the area. The problem of flooding here is now permanent,” he said.
He, besides, emphasized the need to make proper and scientific networking of the small drains, master drains and the channels. “De-siltation of the drains, proper maintenance and networking of the drains are must to control the flood in the city,” he said.
Bhagawati gave the example of Deepor Beel to illustrate his point. The beel was spread over 40 square kilometres 50 years ago. Now, it is limited to just 4 sq km in winter (in summer, it is 10 sq km).
A report by Guwahati Metropolitan Development Authority said the drainage system in Guwahati collapses if the Bharalu river fails to carry excess rainwater. “The natural topography of the city guides the flow of rainwater towards Bharalu and Basistha channels. Due to siltation, the Bharalu riverbed has considerably risen,” the report said.GMDA also emphasised the need to increase the discharge and retention capacity of the existing drainage system.