Guwahati, Friday, August 18, 2017
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Temporary measures can’t help solve city’s waterlogging problem
Ronjeev Das

 
 The current spell of rain-induced floods in several areas of Guwahati is a grim reminder of the crumbling civic infrastructure in the city. It also points at the lack of sincerity and professionalism on the part of the authorities concerned in tackling this problem the residents of the city have been facing for long. The rain-induced flood problem of Guwahati with which the citizens of this proposed smart city are familiar, has been deteriorating primarily because of four major factors. These are: 1:– We are not sincere enough to tackle this problem once for all. We believe in makeshift arrangements. We the citizens, the print and the electronic media, the administration, the political class and many others prefer to discuss vociferously the waterlogging problem only in the months of June, July and August. The issue dies down after September. 2:–It is absolutely true that the city has been witnessing rapid shrinkage of low lands or water bodies in and around the city due to rapid urbanisation. 3:– Agitations demanding land pattas that encourage earth-cutting in the hill areas of the city are proving to be disastrous for the city’s drainage system. 4:– Non-diversion of the Bahini river and gradual shrinking of water storage capacity of the Bharalu river as well as improper and unscientific drainage system of Guwahati, which is surrounded by a vast tract of hilly terrain.

Both long-term and short-term measures must be worked out to draw the roadmap for construction of ‘under-earth’ and ‘overhead’ rainwater storage spaces for harvesting rainwater. As a long-term measure, the Deepor Beel, a major storm water storage basin, has perennial water spread area of about 10.1 km2 and extends up to 40.1 km2 during floods. The main sources of the Deepor Beel’s water are the Basistha and Kalmani rivers and local monsoon run-off between May and September. The Deepor Beel drains into the Brahmaputra river, 5-km northwest, through the Khonajan channel. The Deepor Beel could play a major role in mitigating the waterlogging problem in the city, if the rainwater coming down from the Meghalaya foothills could be diverted to it, instead of allowing the same rainwater to make its way into the city.

During maximum flooding, the Deepor Beel gets four metres deep. However, during the dry season, the depth drops to about one metre. The threat to its existence and sustainability could be easily analysed from the gradual decrease in the wetland area from 33.5 per cent in 1990 to 21.1 per cent in 1997 and then to 19.4 per cent in 2007. The main reason behind the reduction of the Deepor Beel’s area is large-scale encroachment by various agencies like the BSF, the Railways, brick kilns and other private parties, etc. Experts should explore if the Deepor Beel could be re-engineered and dredged to a suitable depth so as to accommodate at least three times the length of the flooded Bharalu within itself.

As the Beel is surrounded by steep highlands on the north and the south with the Rani and Garbhanga hills in the backdrop, extensive studies should be taken up to enlarge the Deepor Beel wetland area of 410 hectares by at least 25 per cent, if necessary, at the cost of land acquisition.

Dredging of the Bharalu bed and subsequent widening of the river is a very important step towards creating a solution to the problem of waterlogging in Guwahati. We are fortunate to have with us the 6.4 km-long Bharalu canal.

But, unfortunately, the Bharalu is not in Europe; it’s in Guwahati. So, it remains a neglected entity without water-scooter, water-taxi or canal-bus service. The Bharalu’s bed becomes so shallow in the months of February and March that school children are seen playing cricket on some locations of the river. Instead of utilising the Bharalu’s potential to solve the city’s waterlogging problem, it has been used for years as an alternative location for garbage dumping and encroachment. We all should come forward to redesign the Bharalu from the RG Baruah Road to the Pragjyotish College with proper gradient and other technical parameters so as to create a technological marvel in such a manner that the river can accommodate within it at least three full-length and flooded Bharalu rivers.

The ‘water-storage capacity’ of the Bharalu canal could be close to 1.5 million cubic metres. If the Bharalu is widened by 15 metres on an average and its bed is dredged to maintain an average depth of 15 metres for its reconstruction as a rainwater reservoir, it would help solve the city’s waterlogging problem to a great extent. Going by the rough estimate, if the Bharalu is widened and deepened, the Bahini is diverted and the Deepor Beel is enlarged with the above -mentioned parameters in mind, even 10 days of heavy rainfall for 3-4 hours a day would fail to make any impact even on the low-lying areas of the city in terms of waterlogging and artificial flooding.

The entire process of making the city free from flash flood, including that of diversion of the Bahini river and widening as well as dredging of the Bharalu and enlargement of the Deepor Beel area to at least 550 hectares, should essentially be a part of the effort to upgrade Guwahati into a smart city.

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