Well We can fight and prepare ourselves for such disasters its need a good planning and well control on administration of BMC.
Rehabiliate the Slums of Mumbai to suburbs with Minimum Areas as per SRA.
remove the encrochement near drainage, rivers , nallahs and Railway Tracks and strict rules to be made if encrochment takes place again after removal the ward office is responnsible and suspend them immediately once or 2 if Govt. will take action everythign will fine.
we have to make a special rules for peoples who caught under corruption and punishment to be decided not by court may be by vigilance commission or by a higher authority.
BMC and other authority to seat together like Power Supply agency Gas supply agency and make a plan for their pipelines and cable lines, so they can do their work without harming the roads and drainage everytime,
make an authority who is responsible for management and if he fails decide a punishment for that.