Nearly all rivers have a lower, middle and upper course.
Upper Course:
A river always starts from the upper course of the river which can be found at glaciers, springs, rills and lakes that can be found at the top of mountains. The river can create waterfalls where it carves out layers of soft rock and leaves a cliff of hard rock standing.
Middle Course:
When the river descends to lower levels, it runs more slowly over the gently sloping land of its middle course.
Its current no longer has the force to carry stones or gravel.
This material drops to the riverbed, where it forms bars of sand or gravel or builds islands.
It consists of rapids, waterfall, canyon, alluvial fan, tributary and intermittent stream.

Lower Course:
As the river flows downstream it reaches the still gentler slope of its lower course.
It drops more of its load than it did upstream and begins to build up its bed instead of tearing it down.
The valley has been eroded into a wide plain. The river swings in great S-shaped curves, forming loops called meanders.

Upper course features:

Spurs: An interlocking spur is a natural feature which occurs in a river's upper course, where upward erosion is the dominant force in determining the river's course.

Potholes: Potholes are formed when rock fragments are dragged along the river bed or against river banks known as corrasion or abrasion and it is particularly effective during a flood.

Rapids: A rapid is a section of a river where the river bed has a relatively steep gradient causing an increase in water flow and turbulence. Rapids occur where the bed material is highly resistant to the erosive power of the stream in comparison with the bed downstream of the rapids

Waterfalls: Waterfalls are sudden, steep, vertical flows of fast-flowing water falling from great heights. Waterfalls are normally formed in two ways, erosion of rocks of different resistance or faulting.
1st Way: Waterfalls are formed through erosion of rocks when the river flows erodes the less resistant rocks more rapidly and this causes a change in the gradient of the river cause and over time the river would plunge from a great height. This repeated pouncing will leave a depression which would deepen as rocks and boulders swirl around at the base of the waterfall creating a plunge pool.
2nd Way: Faulting involves the movement of rocks along large cracks in the Earth's Crust. This movement may result in the lifting of one block of land above the other. When a river flows down from the edge of uplifted block, a waterfall and a plunge pool are formed.