It becomes narrow and steep-sided in the upper course due to vertical erosion.

Find out more about the long profile of a river.

The transportation of dissolved chemicals. This varies along the river depending on the presence of soluble rocks.

Find out more about how rivers transport material.

Social costs of constructing dams and reservoirs include:

• the displacement of people due to flooding
• the loss of cultural heritage
• the resettlement of large numbers of people
• the health and well-being of affected populations both upstream and downstream

Find out more about hard engineering.

Deposition occurs whenever a river loses energy and velocity falls.

Find out more about river deposition.

Water flows slowly over shallow areas (riffles) in the riverbed and faster through pools, deeper sections of the river. This leads to helicoidal flow that corkscrews from one bank to another. Fast flowing water on the outside bank causes lateral erosion through hydraulic action and abrasion which undercuts the bank, creating a river cliff. The eroded material is then deposited on the inside of the next meander where friction slows the flow, creating a slip-off slope.

Find out more about meanders and oxbow lakes.