* Stop building anything in floodplains or other places subject to flooding.
* Wherever an increasing pattern of incursion flooding from waterways is appearing over developed land, pull back to higher ground. That means don't rebuild structures there, move people somewhere else by giving them enough funds to build or buy an equivalent property somewhere safer.
* Increasing floods due to rainfall or other causes may need different responses, such as creating rain gardens and marshes, or upgrading water management infrastructure.
* Provide incentives and assistance for people currently living or working in flood-prone areas to move into safer areas before a flood forces them out and requires expensive emergency measures. This requires analyzing how many homes and businesses are in an area of responsibility, how many people they are, whether the population's needs are currently being met, how many replacement structures will be needed, and where would be a safe place to put those.
* If you live in a flood-prone area, move elsewhere as soon as it is feasible for you to do so. It will be better to move before you are driven out (or possibly killed) by rising waters.
* Restore wetlands and other riparian features to reduce the tendency to flood.
While these would better be done on a national level, any individual town subject to flooding can do it on a local level. Zone flood-prone areas for water management instead of building. Identify safer areas and provide incentives for people to build there instead. Assist people in flood-prone areas to move out of them. This will save you a ton of money and trouble.