River flow, erosion, transport & deposition
Go right inside a river channel and study the physics of moving water. In this AS lesson we first learn to measure discharge with Q = area × velocity, working it in cumecs. Then we meet the three types of flow — smooth laminar, erosive turbulent, and the corkscrewing helicoidal flow that shapes every meander. We watch a river erode its channel by hydraulic action, corrasion, corrosion and attrition; transport its load by traction, saltation, suspension and solution; and deposit whenever it slows and loses energy. We finish by comparing two channel patterns — meandering and braided — and see how a river's discharge decides which it becomes, using the Zambezi, Kunene and Namibia's ephemeral rivers.
By the end you should be able to (NSSCAS Geography (AS) 1.3a):
- explain the difference between laminar, turbulent and helicoidal flows in a river channel
- explain the processes by which a river erodes its channel with reference to hydraulic action, corrosion, corrasion and attrition
- explain the processes by which a river transports its load with reference to traction, saltation, suspension and solution
- explain where and why deposition and sedimentation take place in a river channel
- explain the difference between a meandering and braided river channel