‘Rainwater can’t flow out as drains choked’: Gosain
Gosain said stormwater drains need to be cleaned at least biannually for free flowing of rainwater.Updated: Jul 24, 2020 02:53 IST
Delhi is losing its capacity to handle monsoons, even when it is rain-deficient. This is mainly because Delhi has a drainage master plan from 1976 that does not factor in the construction boom in recent years. AK Gosain, professor of civil engineering at IIT Delhi,who submitted a drainage master plan to Delhi government in 2017, tells Jayashree Nandi that Delhi can see a calamity anytime. Edited excerpts:
First, paved area in Delhi is on the increase. The run-off from paved area is far higher than natural areas. For example, for one unit of rain, a paved area will generate 95% of run-off compared to 50% for a natural area. With a rise in paved area, we are seeing a rise in the volume of water that needs to drain. Second, in Delhi we get rain for four months; the drains are supposed to be dry for the rest of the year.
But no drain is ever dry. They carry sewage instead. Third, stormwater drains need to be cleaned at least biannually or rainwater cannot flow freely.
The drain was choked. It should have been de-silted. Water level kept going up, eventually washing away houses. We need to check if they were authorised. And why were they constructed on a drain?
Yes there are many locations like that, which are in a depression. These cannot drain naturally. The water has to be pumped out immediately.
We have completed our job and its up to the government. The plan captures all the issues with flooding and drainage I have mentioned.
If the floodplains are constricted, then the level at which water will pass through will be higher. So when there is a big flood, embankments will breach and there will be calamity. Also, if the water level in the river is high, all the drains flowing into it will be surcharged and there will be backflow.