Meanders are formed by a combination of erosion and deposition in the mature and old age stages of a river.
An example of a meander can be seen in the middle and lower course of the Rivers Shannon and Boyne.
A
Outside of bend – river cliff
Inside of bend – point bar
Formation 1
Erosion
Water flows more quickly on the outside of the river bend. The river erodes the bend by a combination of hydraulic action and abrasion.
2
Water flows more slowly on the inside bend of the river. Material is deposited on the inside bend as the river loses energy here.
Slowest current on the inside of a bend
A B Neck of meander
Deposition Strongest current
Fastest current on outside of a bend
10
Cross-section through a meander Point bar
Deposition River cliff Undercutting Slowest current Fastest current Erosion B
Looking at this photo, where is erosion and deposition occurring in this meander? What evidence can you see to support your opinion?
Managing information and thinking:
1. Explain why wide valleys are found in the mature stage of a river. 2. Why is the soil on a flood plain good for growing crops? 3. Explain why, in your opinion, it would be important to know if your land is on a flood plain before building a home or business?
4. Describe with the aid of a labelled diagram how a meander is formed.
