A 15m rope will be only just be enough then, does anyone have a longer rope? There do look like a few options for crossing it though with trees and a narrower if somewhat gulleyed section further on either a bit of a walk or tarzan with a bike?
"Crossing the Abhainn Poiblidh by a ruined house. This was probably a shepherd's dwelling. Crossing rivers safely is a vital skill in the Highlands, bridges can be a luxury, and water levels are often very high."