In one of the most devastating floods in South India, the metropolis of Chennai had the worst shock of its life. Unbridled expansion of the city into areas vulnerable to floods is stated to be one reason. However, there is much beyond this, and there are lessons aplenty to be learnt for all the fast-expanding urban areas of India from the Chennai deluge.
Flooding in urban areas can be caused by flash floods, coastal floods, or river floods, but urban flooding is of a different kind. Urban flooding is specific in the sense that the cause is a lack of drainage in an urban area. As there is little open-soil that can be used for water storage, nearly all the precipitation needs to be transport to surface water or the sewage system.
High-intensity rainfall can cause flooding when the city sewage system and draining canals do not have the necessary capacity to drain away the amounts of rain that are falling. Water may even enter the sewage system in one place and then get deposited somewhere else in the city on the streets. This is more or less what happened in Chennai.
As what the Chennai deluge has shown us, urban floods can upset the daily life in a city. It can happen in any other towns or cities in the country. Roads can be blocked, people cannot go to work or to school. The economic damages in the Chennai case are high, but the number of casualties is not that high, because of the nature of the flood. In urban floods, water slowly rises on the city streets. When the city is on flat terrain, the flow speed is low and you can still see people driving through it. The water rises relatively slow and the water level usually does not reach life-endangering heights in many cases.
(To read the full article… subscribe the January issue of Safety Messenger Magazine 2016)