We got feedback from our design submittal with the following technical advice:
“Rainfall intensity is normally dependent on the time of concentration. Confirm that time of concentration is approximately the same for both pre- and post-development conditions to document that the rainfall intensity does not change.”

As I interpret the feedback they want us to show if the rainfall intensity changes pre and post development? How do we do that? The area has pretty much the same ground conditions post development, just more buildings with roof instead of asphalted areas. I do not believe that it will have an impact on the weather.

Or have I interpreted it wrong?

Note our project is located in Sweden, so we cannot use existing American data.

Thanks in advance ! /Veronika