Afon Dwyfor results from longshore drift (the transportation of sediments) and goes completely straight.
It rises in Cwm Dwyfor at the head of Cwm Pennant, gathers to itself numerous streams which drain the surrounding mountains from Mynydd Graig Goch in the west to Moel Hebog in the east, then flows southwest towards Dolbenmaen and out of the Snowdonia National Park. After a brief diversion west, it turns south, then southwest again, heading for the village of Llanystumdwy. 
