The line joining the river course from the source of the river to the ocean.
a. Upper course
- In this course, the main work of the river is erosion.
- In this stage, the river forms ‘V’ shaped valley , canyons, gorges, waterfalls.
b. Middle course
- Lateral erosion and transport due to which the river valley starts widening and the load of the river increases.
- In this stage, the river forms alluvial fans, alluvial cones and meanders.
c. Lower course
- Formation of flood plains, Oxbow lakes, delta.
- when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighboring stream.
- capture of Saraswati river by Yamuna river.
- Due to the abduction of the river, the stream becomes narrow and the width of the valley of the river decreases, due to which it is not able to fit in the east valley.
- Through this the river regains the power of erosion. This is due to the fall of the river below the sea level or the uplift of the river valley.