Does this sentence sound dirty?

I mean, yeah, out of context someone with a dirty mind might think this is about climaxing. Other people might just be confused as to what is being discharged.  But in context it would be pretty clear that this sentence refers to water in a flood. Most people don't automatically associate the word "discharge" with something naughty. 

there are plenty of normal statements that sound dirty when taken out of context. there's a type of joke - "that's what she said" - which is heavily used on The Office (the American one) that draws attention to this phenomenon for comedic effect. example: "Hold it in your mouth if you can’t swallow." ... "That's what she said."

Just wait 'til you start reading about [groins](https://en.wikipedia.org/wiki/Groyne) (if your reading material uses U.S. spelling). They set up some pretty catastrophically dirty sentences, several of which I was supposed to read out with a straight face one day in geography when I was still in school (I did not succeed). To answer your actual question, yes, it's the sort of sentence I would have quoted out of context to friends when I was a 12-year-old boy and laughed at my fearsome wit.

It’s fine. What’s dirty is just in the mind of the reader. In context it’s not dirty at all but some people’s minds just love to go there

I am familiar with the technical context so I wouldn't have thought of it as dirty, but I can see how someone might.

It's fine.

A bit, yes.

Maybe to some people. Lots of things can sound dirty out of context. Discharge however is way too clinical and unsexy to ever sound dirty to me.

It only sounds dirty if you are under 13 years old. For the rest of us it sounds perfectly normal.

No

It seems fine, though unless you are talking about water draining from, say, a lake or a dam release, I might be tempted to use "peak flow" instead. If you're talking about release of water from a dam's overflow system, "discharge" is probably the perfect word.

Not going to lie I chuckled a little reading it

If you’re British, anything can sound dirty.

It's a bit of a stretch.  And after typing, I see what I did there.