Any advice about roof runoff which shoots
over eavestroughs?

Problem occurs at two corners of a steeply gabled
roof over a deck. Rainfall collects in such volume
that at the corners it shoots a foot or more horizontally
before falling 18 feet to the deck, where at one corner it
damages the stained railings, and at the other has
encouraged rot in several siding boards below the deck.
We added eavestroughs and a downspout elsewhere,
curing a similar problem, but do not know what to do
about the corners, where damage now is worse after
an unusually rainy summer.
--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)