Stainmore is drained by the River Belah and the River Balder. It is crossed by the Roman road from Bowes to Brough, now part of the A66, and formerly by the Stainmore Railway. Each of these lines of communication has made use of the relatively low broad saddle between the higher hills to north and south which is commonly referred to as the Stainmore Gap. The summit of the former railway is around above sea level, though the roads climb to slightly higher elevations. The Gap is coincident with the Stainmore Summit Fault which throws the relatively flat-lying Carboniferous rocks of the area down to the south. It acted as a conduit for Lake District-originated ice to pass eastwards during one or more glacial periods.