How do I calculate a sufficient pipe diameter, for handling a given amount of impermeable pavement?
A general answer is best.
In my particular case I have approximately 675 square feet of tile roof and driveway which drain to the front of a garage. The garage door is the low spot. An additional 650sf of neighbor driveway more or less sheets into this same area. To add to the calculation difficulty it's likely that 650sf will be changed to a permeable pavement. Area is San Francisco Bay Area, California USA.
From the low point I could run a pipe about 70 feet in length with a drop of 12 inches, to drain the water by gravity (1.4% slope on average with one cleanout). Or I could go 10 feet over and down at 4% slope to reach a sump in the home's basement. Or accept a drainage contractor's bid (total $30,000) and have this water pumped uphill to the curb about 2 feet.