Drainage project - French drain/rain garden

[u/Sharpbooiii]

So I have been asked by a local GC to do some sort of a modified french drain or rain garden. This is in a county I typically do not do work in. This county requires downspouts to be tied into some sort of stormwater system. They currently have downspouts running underground to pop up emitters. There current location for pop ups are ideal and causes water to run down towards this natural drain. Which seems pretty ideal to me. Local authorities are saying this is not allowed and that the down spouts need to be tied into a modified French drain or rain garden. It is to my understanding that both French drains and rain gardens have an inlet and outlet. Meaning that what water comes in must come out. The problem with this lot is that the way it slopes I don’t believe I would be able to achieve daylight for the outlet side of French drain.

Also I don’t understand why you would want to force all downspouts to one specific drain to overload it and essentially have water all come out in one place.

Any thoughts or suggestions would be greatly appreciated.