I empathize with you (my dad lives in chennai, and we are yet to make contact with one of my friends). The worst seems to be over, so hopefully the city will be fine.

I moved out 3 years ago, so I wanted to reply to the fiber/subway part of your comment. Those two were absolutely essential, and a better drainage system would not have helped much in the floods. In the last 10 years or so, there has been ridiculous construction on what used to be lakes, and today the worst affected areas are those. See my comment here on HN from almost 2 years ago . (https://news.ycombinator.com/item?id=7881544). This was waiting to happen, but not because the drainage system sucks, there is literally nowhere to drain the water off to.