As a river moves from higher ground onto a flatter plain, it loses energy. This causes the river to deposit the heaviest sediments of its load on the riverbed. As these sediments build up, they form alluvial fans, which can cause the river to split into more than one channel, forming a braided stream (Fig. 8.18).
Islands
River
Fig. 8.18(a) Braided stream.
Alluvial fans/ braided stream
Fig. 8.18(b) Braided stream: notice the alluvial fans in the middle of the river.
Fig. 8.18(c) Braided stream: notice how the river has been divided into two streams before meeting again.
CHECK YOUR LEARNING
1. Explain the difference between vertical and lateral erosion. 2. Why does the river have an increased volume in the mature stage? 3. Explain the difference between ‘bedload’ and ‘suspended load’. 4. List and explain two reasons deposition may occur on a river. 5. Describe what a meander looks like. 6. How does a river cliff form? 7. How does a point bar form? 8. What is a braided stream and how does it form?
