How do i flood a place, and then the flood clear?

I wanted to make a game. where the city would flood. this would be a zombie game of course. but problem is, i have no idea how to do it. ill give you various examples of what i'm talking about. reason to die (1 of though's series) (what ever floats your boat) i think i know a few more but the titles are stuck in the back of my head. back to the topic. the script. i know i don't need a brick to do this, or do i? anyways. what should this script look like. I'm talking about it to flood. and then after a few minutes. clear away the water. i'm looking for a positive response. i hope this script isn't as long as i'm thinking it might be. i don't want to get a warning again.

quote "I dont want to get a warning again" this is what i meant. This question is obviously closed. just as a note to future closings. this is a Q and A site. I made a question. and i got a answer. except the answer was a warning. 2nd below me, this comment "This isn't a request site" i'm not begging you for a script. you have the choice to say no. you have a choice to lead me to the answer threw a wikia. This is the end of my edit. my wish. is to change to rules. this is very offensive to me because i enjoy building to games. and when i get "This is not a request site" that's offensive. because, This is the only place i know i can learn this information. i'm sorry if this edit offended you. but this is speaking from my heart.