The best is to have a wide scupper 12 or wider so leaves and debris will wash through the scupper instead of clogging it.
How to make a gutter scupper.
Scuppers are a very effective way to channel water off a roof.
Gutters collect leaves and stop the flow of water.
The scupper and gravel stop flanges are nailed to the blocking.
Scuppers can let the water drop off the roof to the ground or can lead into a gutter system.
The drip edge of the fascia should extend over the back edge of the gutter by 1 minimum.
The scupper may channel water off the roof into a conductor box with a downspout or a gutter or with overflow scuppers it may let the water run freely down the side of the building.
The gutter should be allowed to move independently of the fascia gravel stop.
In stead of using common elbows under this split copper gutter expansion joint i made this custom scupper or tray that narrows from 9 down to 5 wide at the house with a reducer installed at the back priced at 25 sq of 20oz copper used to make this.
Gutters scuppers and roof drains oh my a well designed and functioning roof drainage system is essential to the long term integrity of your properties and their surroundings.
This detail shows a scupper used in conjunction with a gutter.