Another word for gutter.
Gutter from one roof to another.
The water is allowed to run on the roof surface and is collected by the lower gutters.
As part of this system malarkey recommends against the drainage of one roof directly onto another especially because the lower roof often has less slope than the upper.
A hole at the bottom of the gutter or an open gutter end will just splash water around in a heavy rain.
A steep roof covering a house has a larger area and collects more rain than a shallow roof on a house of the same size.
Note also that the valley also sheds its water down the roof surface as well as opposed to into the gutter.
Measure the area of each roof section to calculate gutter size.