Flood plains provide enough of a food surplus to feed a few hammer tiles; putting farms on them might be excessive. Especially if it means you need to leave some of them idle:
Every flood plain you work is a good tile (even if the health cap matters, it's still 2.6 food, 1 commerce and whatever improvement you have), every flood plain you don't work is horrible (-0.4for nothing).
Don't worry aboutas long as you have the
surplus to counter it.
Remember, an unhealthy floodplain is at worst food-neutral (2 food = 1 pop), so unhealthiness is never a real problem.
How do you tell what is flood plains and what is not?
What can be done to alleviate the sickness due to living near flood plains?
Anything?
Thanks
Mk