This video uploaded by Indian Express Online, explains that it could be a man-made one. While some experts speculated that it could be because of strong El Nino (prolonged warming in the Pacific Ocean) and upper air divergence, it turns out the reason behind the calamitous flooding was something done by the authorities who released 30,000 cusecs from Chembarambakkam reservoir into the Adyar river, deluging the banks and the neighbourhoods. Also, poor urban planning may also be the reason behind this. Check it out!