The most common and most likely answer to this crossword clue is the 8 letter word FRESHETS
I've seen this crossword clue in The Daily Telegraph
F
R
E
S
H
E
T
S
Buddy explains!

The straight part
We know that "floods" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case floods = freshets.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does FRESHETS mean?
FRESHETS noun- A flood resulting from heavy rain or a spring thaw.
- A small stream, especially one flowing into the sea.