Potholes. Potholes are cylindrical holes drilled into the bed of a river that vary in depth & diameter from a few centimetres to several metres. They’re found in the upper course of a river where it has enough potential energy to erode vertically and its flow is turbulent.In the upper course of a river, its load is large and mainly transported by traction along the river bed.eanders are bends in a river that form as a river’s sinuosity increases. The sinuosity of a river is a measurement of how much a river varies from a straight line. It’s a ratio between the channel length and displacement (straight line distance) between two points in the river’s course: