The River Yarty is a river in east Devon, England, near the boundary with Somerset and Dorset. The river is about 26 kilometres long. The source is in Staple Hill in the Blackdown Hills. It flows on a roughly southern course through Bishopswood, briefly forming the boundary between Devon and Somerset, then between Devon and Dorset following a tripoint of all t…The River Yarty is a river in east Devon, England, near the boundary with Somerset and Dorset. The river is about 26 kilometres long. The source is in Staple Hill in the Blackdown Hills. It flows on a roughly southern course through Bishopswood, briefly forming the boundary between Devon and Somerset, then between Devon and Dorset following a tripoint of all three counties, through Marsh. It continues to form a river valley for much of the rest of its course, passing between Yarcombe, Stockland, Dalwood and Membury until it meets the River Axe just southwest of Axminster, which continues to the English Channel.