Why Mumbai only ? what happened there can easily happen elsewhere in India - Chennai, Bangalore, Hyderabad, Kolkata - when nature strikes, it is bound to be a telling blow as it happened in Mumbai
In Bangalore or Chennai for instance, even if 20% of the rainfall occurs, the cities for sure would go underwater (literally)!
it is not the govt alone that should act, every tax-paying citizen ought to do some rational practical soul-searching and come up with solutions
1. the incredibly voluminous amount of garbage that lies unattended to in all our cities - do we have an action plan for them ? No
2. is there a blueprint/model to understand how much of garbage we generate in big cities every day/week/ month and what happens to them ? No
3. Is there a model projecting the rate at which we would be generating garbage in the next 10-15 years vis-a-vis population growth ? No
let us address the above three questions in detail/ depth and then come up with workable plans of action and implement them with members of an executive committee chosen from the public at random, the judiciary and the armed forces overseeing the implementation - only then will something happen