I think your answer would be huge. Because we already know that the torrent of water rushed down the street, so we really don't need the adjective huge to describe it.
The unnecessary adjective in the sentence is "huge".
Explanation:
"Huge" is redundant in this sentence because it means the same as "torrent". On the one hand, "torrent" refers to "a strong and fast-moving stream of water or other liquid" or to "an overwhelming outpouring of (something)". On the other hand, "huge" means "extremely large, enormous". As you can see, they both make reference to the same meaning component "something being extremely big and of great importance".
