Economic benefits of constructing dams and reservoirs include:

• boosting tourism e.g. the local economy of Kielder has been boosted by £6 million thanks to the construction of Kielder Dam
• they can be used to produce electricity by passing the water through a turbine within the dam

Find out more about hard engineering.

In the upper course, the river erodes its bed by hydraulic action and abrasion. As the river flows downstream it is joined by tributaries, increasing the volume of water, velocity and therefore its erosive power. This enables it to cut a deeper channel as it flows downstream.

Downstream, the channel becomes wider as the gradient becomes more gentle leading to less vertical erosion. By the middle course of the river lateral erosion becomes the dominant type of erosion. The channel becomes wide because of lateral erosion.

Find out more about the cross profile of a river.

Examples include:

• it can reduce habitat diversity when hillsides are covered in tree
• it can lead to acidity in the soil
• the loss of farmland

Find out more about soft engineering.

Natural ways flood risk can be increased include:

• heavy rainfall caused by depressions causing heavy, continuous rain which saturates the soil. The land can no longer absorb water as it is saturated increasing surface run-off, higher river discharge and flooding.
• sudden downpours occurring following a very dry period can lead to flooding because the surface is baked hard. Surface run-off occurs as water cannot infiltrate leading to higher river discharge and flooding.
• sudden snowmelt releases stored water that flows over the land as surface run-off
• the loss of vegetation cover through drought or disease can lead to flooding as less interception occurs so more precipitation reaches the surface leading to increased surface run-off.

Find out more about human and physical causes of flooding.

Solution (or corrosion) is when acidic water dissolves rocks such as chalk or limestone.

Find out more about river erosion.