STORM WATER DRAIN PROJECT – IIT MADRS SHOULD CLARIFY

Presently I am not a resident of Chennai. But I had lived in Chennai for more than five years. So I know its problems to certain extent and the from the media reports I am under the impression that the present Govt. is taking some useful and beneficial steps to alleviate the woes of Chennai. The writer's opinion seems to be contrary. In this regard more unbiased opinions from the residents of Chennai will give a clear picture. So may I invite more residents of Chennai for their opinions. more  

I am not an expert in hydraulic/civil engineering, but here is my take based on my general engineering background. Chennai has certain peculiar characteristics. It is almost flat and almost at sea level. Solutions that work elsewhere will not work in Chennai. Waterlogging takes place mainly because some areas are lower compared to those around (perhaps because they were lakes long back and have been built over). Water tends to stagnate in these areas and unless the drain system is designed correctly, flooding even after a light rain is inevitable. Only a micro-survey can identify such areas. Embedding rainwater harvesting pipes in the storm water channels may help somewhat but during rainy season, water table rises in most Chennai localities and soaking into the soil will become very slow and cannot be depended upon. Storage ponds are normally created at places which are at a naturally lower level. Chennai corporation may create such ponds in OSR lands wherever feasible. Using pumps to fill storages will be cost-prohibitive. But I believe that there are some pumping stations already which help to lift the collected water and pump it into natural drains like Coovam river or manmade channels like the Virugambakkam canal. The problem is that they can get overwhelmed during heavy monsoon periods, or the pumps may stop due to electricity supply interruptions. Unauthorised diversion of sewage into stormwater drains and accumulation of garbage in the existing drain channels is another ongoing issue. If we pump this kind of polluted water, even the storage ponds will get polluted and become mosquito breeding centres. I do not know whether IIT Madras was involved in the detailed engineering of the current construction work of drains. But as the post says, they should clear the air about it and must insist that they should be allowed to do a comprehensive (not piecemeal) study which includes the study of capacity of existing natural and manmade drain channels and work out a solution. more  

Agreed with your suggestion more  

Manuel Aaron: I am no expert on Storm Water Drains and whether they work or do not work. But I like to be informed by experts of the realities in our City. The technical comments by Mr C.U.Chandrashekaran and Mr Thamarai Kannan are illuminating and tell me how ignorant I really am with regard to flooding. However, the post by Mr N.S.Venkataraman 'exposes' all the ills of Chennai, ropes in IIT, Madras, and concludes by asking IIT, Madras, to protect its reputation! Fortunately, I live in a part of the city, Shastri Nagar in Adyar, where the recent heavy rains did not cause any flooding at all. In 1943,44 when there was a big flood in Madras, our family lived in Kariappa Mudali St, Puraswalkam near Thana Street. I remember watching our father swim in about 5 feet of water on our street to fetch food for the family. There were no orange colour boats for citizens' safety. When there was a Japanese Air Raid on Madras during World War II, the air-raid warning Sirens failed to wail. Later the Enquiry revealed that the batteries of the sirens had been affected by the flood water and nobody had bothered to check the batteries of the sirens. That was British Raj!! more  

What I forgot to add is that excess water should be pumped and stored in new water bodies to be created outside city limits. My assessment of the drainage rate was wrong. However, any civil engineer can very easily calculate the evacuation rate, once a 3d mapping is completed, using readily available software. more