Here is a good example, I think, of how cloud shadow can look like dark flood waters:
When we were marking land scars from crop burning, I dutifully marked around a “dark” perimeter. But one of the guys commented about cloud shadows-- which I hadn’t thought of on sat images. I’d marked these incorrectly!
On the above URL, I think it is cloud shadow because the darker areas don’t look the same as other tiles with water. The “darkness” affects treetops and streets but is more a blackness (absence of light, rather than a covering of muddy water). Going just to the next tile, there’s sunlight and no evidence of flood waters.
Note: The area I’ve been in has not had extensive flooding, except near bayous.
Here is the same subject from Louisiana Flooding campaign we did.