Evanton is more or less enclosed to the northeast and the southwest by two rivers, the Allt Graad and the River Sgitheach. The Allt Graad, sometimes called the River Glass, is a river that flows from Loch Glass, near Ben Wyvis, for 9 km (5½ miles) until it passes the northern end of the village, and empties into the Cromarty Firth. However, approximately before it reaches the Cromarty Firth, it passes through the Black Rock Gorge. The latter is a few hundred metres in length and reaches 36 metres (120 ft) in depth.