Many areas of the Guwahati city reel under artificial floods even after a small shower during monsoons. Guwahatians will not get any respite from it in the near future, because no plan has emerged to tackle the basic problem till now. In order to understand how big this problem really is in the context of flooding issues of some cities around the world, we may delve a little into how some mega cities are tackling their flood problems � their magnitude and the related environmental issues, so that we may be able to deduce a common thread for a solution to the problem in Guwahati.
The New Orleans City, USA, was founded in the 18th century. The typical feature of the city is that the central portion of the metropolitan New Orleans is completely surrounded by water � two lakes and wetlands in the north, east, west, and the river Mississippi in the south. Much of the land area between these water bodies are below the sea level and the city no longer has a natural outlet for flowing surface water. As such, rainwater occurring within this area must be removed through �pumping� only. There is a threat of flooding from the Mississippi and the lakes, so kilometres of levees (embankments) have been built to check rising river and lake waters. These levees further restrict any floodwater from going out of the city.
By 1980, the city boasted a system of 20 pumping stations with 89 pumps, with a combined capacity of 59,210,000 L/minute of pumping. By 2005, the number of drainage pumps have been increased to 148 with a consequent increase of pumping capacity. A truly mindboggling exercise, indeed.
For this vibrant city, pumping effectively is the key to its life � it is like breathing. People do not even feel that water is constantly being pumped out of the city!
Nearer to our city is Kuala Lumpur. The city experienced severe flooding due to Klang and Gombak rivers up to 2003. The city has constructed a 9.74 km-long tunnel for holding one million cubic metre of floodwater and to release it in the downstream of the city whenever possible. Twenty-three pump stations were installed to ensure that the floodwater inside the tunnel can be emptied quickly during very heavy flooding. A part of the tunnel, a three-km stretch, has a double motorway during the dry period, relieving the traffic on the highway!
The city of Venice is sinking slowly but the Adriatic Sea is swelling � it is predicted that sea level will rise by a foot by the end of the century. But the residents of this 1500-year-old city are not going to abandon their beloved city. So they have come up with a mindboggling plan to pump 150 billion litres of sea water into the rock strata beneath the city over a period of 10 years through a series of wells installed all around the city. Injecting billions of gallons of sea water could inflate the porous sediments under the canal-crossed city, causing the city to rise by as much as a foot by the end of the decade.
Needless to say that Venice resorts to regular massive pumping through a scientific pumping grid.
Singapore, Jakarta and Bangkok resort to heavy pumping to avoid flooding and have placed other innovative measures to mitigate the problem and control flooding.
What Guwahati needs: What Guwahati needs is �pumping�, not by the piddling pumps at Bharalumukh. Also not in the scale of, say, New Orleans, where they pump out 59,210,000 litre per minute (1980 statistics, which have been augmented many times since 2005).
As we have disturbed Nature�s balance by denuding and degrading the hills surrounding Guwahati, the water from these hills flows down immediately after heavy showers, creating flash floods and inundation of areas like the RG Baruah Road, Anil Nagar, Nabin Nagar and Lachit Nagar, etc. When the water level of the Brahmaputra is high and the Bharalu sluice gates are closed, then the Bharalu does not act as a drainage channel anymore. This is the crux of the issue. This huge volume of water which enters the city in a gush must be emptied quickly and effectively by integrated and scientific pumping into the Brahmaputra, not by �pumps� as we commonly understand, but by huge pumps whose outlets will be 5-6 feet in diameter. When in operation, these huge pumps will have an immediate impact on the Bharalu water level. Three pumping stations can be planned on the bank of the Bharalu � one on the west of RG Baruah Road, another on the west of GS Road and the third at Bharalumukh (near the existing small pumps). A fourth pumping unit should be set up in Bahini to pump out the Bahini basin water directly to the Brahmaputra at Bonda. The pumping should be done from deep pumps of suitable diameter, which are constructed like �wells� of river bridges, and connected to the Bharalu for continuous flow of pumped-out water. The pumping complexes must have their own generating sets and must be manned and managed professionally, outsourced to private companies. The pumped water will have to be pushed to the Brahmaputra through huge outlet pipes that will have to be taken along the side of Bharalu, preferably underground, or on tressels as per requirement.
When these big-capacity pumps will operate, the Bharalu water level will come down quickly, allowing the neighbourhood waters to be drained into it from the worst-affected localities. Apart from natural drainage as a result of the primary pumping in the Bharalu, these localities can also have a secondary pumping arrangement along the Bharalu to speed up complete removal of the floodwater from these worst-affected areas very quickly. The success of the project, however, will be directly linked to proper selection of pumps, volume of water to be pumped out and other project parameters by competent and reputed consultants.
But how big should the scale of this operation be? When we see the mindboggling steps taken by cities around the world, our level of pumping and the infrastructure needs for our city are quite insignificant. We are not talking of pumping capacity of over 6.0 crore litre per minute (New Oreans), or a tunnel to accommodate one million cubic metre and pumping capacity to pump out this water quickly, if needed, as in Kuala Lumpur. We are merely talking of four-five primary pumping stations with discharge pipelines of few kilometres up to the Brahmaputra at Bharalu. No one can question the validity of this pumping, because floodwater will only be evacuated in huge volumes by these pump stations.
Other complementary steps to pumping: A seminar on �Development problems of the Guwahati city� organised by the Institution of Engineers held on Sept 4-16, 1982, after proper survey, had suggested connecting the Deepor Beel to the river Kulsi at Kukurmara, as a satisfactory downward grade exists even when the river Kulsi flows at a high level (which is not the case with the Khanajan outlet of the Deepor Beel to the Brahmaputra).Water from the Basistha side along the NH byepass can be diverted to the Kulsi with the Deepor Beel stretch transported over a viaduct, thereby reducing congestion of these areas to a great extent. Diversion of water from the city to the Kulsi will save the Deepor Beel from being polluted from any drained out water from the city.
The Silsako Beel, a natural water body in the east of the city, has a catchment area of 6554 hectares, which include the military cantonment area, hills on the western side, etc. The Beel is practically full to the brim during monsoons due to its own catchment flow. Any effort to transfer water from the Bharalu basin may only add misery to the Silsako area as the Silsako Beel does not drain out to the Brahmaputra when the Brahmaputra flows at a high level via Bonda.
The recent drive by the district administration to clear natural water bodies and the banks of the Bharalu river of encroachment is a welcome step. The administration also needs to be congratulated for better garbage management now. But the natural water bodies existing in the city now can absorb only a small quantity of flash flood water and complement the flood evacuation by pumping. A proper drainage network is essential to drain out the floodwater of the neighbourhood quickly to the Bharalu in all situations.
We have spent crores and crores of rupees over the years to clean up the Bharalu, ignoring the simple fact that for all the crores spent for mere cleaning it up, the same river ceases to be a drainage channel for Guwahati when the sluice gates at Bharalumukh are closed during monsoons! Cleaning up the river is a normal housekeeping operation and not a �solution� to the flooding. We have seen to what unbelievable extent cities across the world go in order to resolve major issues like flooding of their cities and we should only hang our heads in shame, that our people suffer unbearable situation due to artificial flooding year after year because of complete incompetence of the authorities who cannot think beyond cleaning up the Bharalu spending crores of rupees.