JOIN USIs stop-gap desilting the only way to free the city’s roads of perennial waterlogging every time it rains? As long-term solutions such as a comprehensive redesign of the stormwater drains take the backseat, the desilting contractors thrive.
Trapped in peak-hour city centre traffic, Jayanth Rao dreaded that impending drive back home. The drizzle had quickly morphed into a downpour, engulfing the roads ahead in vast sheets of water. Rao knew the water, already knee-deep, wouldn’t drain out in a hurry. As dusk dawned on Bengaluru, and the streetlights went dark in the rains, the dreaded nightmare unfurled its fury.
The big showers are just round the corner. But the recent rains have already exposed the city’s acute inability to quickly drain out the water from its roads and low-lying areas aplenty. As motorists struggled to negotiate the water-logged streets, the civic agencies fumbled for excuses. Out they came with their standard statements: Desilting of stormwater drains, under way.
Desilting, a scam
Stop-gap desilting is a scam, assert people well-informed about the contract system in the BBMP. “Before every monsoon, a crisis situation is created to aid the desilting contractors. Big money is hijacked,” reveals an insider preferring anonymity. That explains why the civic agencies are publicly perceived as totally unprepared to deal with the rains. The contracts are then dished out in haste.
How long should Bengalureans endure this stop-gap crisis management? Are there no long-term solutions at all? Indeed they are. But the one obvious option -- Remodelling and developing the entire 842 km of stormwater drains-- has never been a priority.
Chief Minister Siddaramaiah’s recent statement on the city’s drainage system is indicative of the pathetic state: Only 115 of the 842 km have been desilted and restored with concrete retaining walls. The Palike is now working on an additional 25 km at a cost of
Rs 200 crore. Restoring the entire network would require over Rs 4,000 crore at Rs 7 crore a kilometre.
Drain remodelling
But the remodelling of the drains has been in the pipeline for 11 long years. STUP Consultants Private Limited had completed a survey of the drains way back in August 2005. The entire project to remodel drains along the four major valleys of Koramangala, Challaghatta, Vrishabhavathi and Hebbal was to be completed in the next 18 months.
It is clear that the delay has substantially escalated the costs. Besides, massive encroachments of the buffer on either side of the drains and unregulated inflow of raw sewage into the SWDs have played havoc with the entire network. The natural flow of stormwater from road-side shoulder drains to secondary and tertiary drains is now severely hampered. Result: Roads flood in a flash!
Bengaluru’s very apparent lack of rain preparedness raises a critical question: Can it handle a flood like what Chennai experienced last year? Analysing the city’s rainfall data over several years, the Karnataka State Natural Disaster Monitoring Centre is not convinced. The rainwater runoff (water that drains away) has doubled over the years. That has raised the flooding risk.
Flood vulnerability
One analysis by the Centre shows that 20 mm rainfall for an hour could trigger flooding in many parts of Bengaluru. The capacity of SWDs is quickly saturated during rains as their Maximum Water Level (MWL) gets breached. As former BWSSB Chief Engineer Thippeswamy informs, once the water flows over the MWL, it gets onto the roads and low-lying residential areas. “Houses should be built above the MWL. But that requires proper planning,” he points out.
Roads could be redesigned in such a way that the stormwater actually recharges the groundwater where the rain falls instead of flooding the area. An urban infrastructure expert contends that this will boost groundwater level in the city centre particularly, since the built-up area is more. “To ensure this, a road by road assessment of the SWDs is necessary,” notes the expert, V Ravichandar.
Cylinderical SWDs
In the city’s central business district, roads being upgraded under TenderSURE have cylindrical underground SWDs.
Explains Ravichandar: “These drains of 600mm diameter have chambers at every 30 metre. Through these chambers, stormwater enters. Since the drains are round, there is less friction and can carry silt to a great distance. Traditional drains have flat surface, which needs regular desilting.”
The TenderSURE roads are designed to drain out the storm water within 20-25 minutes. However, in traditional roads without the required sloping, water collects in cavities in the poorly laid asphalt. These quickly become potholes, endangering motorist lives. This cycle repeats year after year. Concerned citizens of this city now seek a decisive shift in policy, a move away from stop-gap drainage solutions that aid only contractors to a more robust system.