I think it's often a combination of the two.
The most flood prone areas near me are the hilly mountainous areas where it can rain a lot. The floods typically happen after longish periods of heavy rainfall.

The point about topography is valid but floods are often triggered by rainfall, at least as the immediate precursor.

From a human perspective they're both extreme weather events, that can cutoff communities and are dangerous. Snow drifts will form by a combination of topography and wind.