For example, gargamel has been 3 years in the making. Steady work, 1 builder (and I assume friends) and it seems, anyways, he has avoided natural runoffs and or worked them to advantage.
Another thing, if a trail Can't be build with the runoffs in mind, then trails here get reworked every few years to allow drainage to fix itself. This is usually a last resort and is almost always because of older trails being built without the environment in mind.