Flooding and game crashes

I had to do some terraforming so I could build on some land in my newest city. What I didn’t realize is that when you terraform is basically just causes the entire area to flood even if it’s above sea lvl. I’ve also noticed that when it rains the games performance drops drastically and usually causes it to constantly crash, idk why rain is in the game in the first place tbh bc it’s a city sim lol and what sucks even more is that you can’t even turn it off. Lmk if anyone else has these issues