Devastation arising from the sea… Why is Cyclone Ditwah so dangerous? Worst flood in 20 years in Sri Lanka, 390+ deaths, 10 lakh people affected, hundreds of people missing – and now due to its impact, the southern part of India is on alert mode. Heavy rain in Chennai, Thiruval and Kanchipuram, 80+ flights cancelled, schools-colleges closed, roads submerged.