HiVirakSenju,
As many questions here this is a very broad and general, not easy to answer briefly and directly without further specifications.
Stormwater drainage planning will be vastly different, depending on climate, amount of rain and expected flood, local regulation and requirement.
My advice is to really utilize all forms of net research, including the internal search engine for the eng-tips forums (bar just below description of this thread, top of this page) before you go further.
I made a quick test search and found a great amount of info probably answering many of your questions, also general planning advice.
You are welcome back with more detailed questions when you have looked into what is already available.
Good luck.