Flooding is a concern no matter what type of foundation you have under your home. However, as the simplest and sturdiest foundation type, slab foundations are mostly unaffected by flood waters. It is likely that you will find yourself more concerned with the damage that the flooding has caused to the structure on top of your slab foundation instead. However, after you have cleaned up, this is actually when you should be checking out your slab foundation for problems.
The major concern you should have about flooding when you have a slab foundation is any erosion that has occurred. If the grade that forces water to drain away from your foundation has eroded away, this will cause drainage issues and eventually foundation problems.
However, a lesser known erosion issue is undercutting. During a flood, the soil is saturated and easily malleable. As such, when the water recedes or is affected by a current, the soil under your slab can be eroded away. This can cause extreme settling, and often does so unexpectedly because you might not notice undercutting right away.
If your slab is not sitting on a stable surface, it can cause settling that can actually crack the slab. This is why if you have had flooding you will want to wait a month or two in order to let the soil fully dry out, then have a foundation inspection conducted. This can check for undercutting and make sure your grade is intact enough. If nothing else, you will want to monitor your slab foundation in the following months to make sure new cracks do not appear on it.