Flooding occurs when the volume of water in a river exceeds the capacity of the channel. The water then overtops the banks and overflows onto the floodplain. Flooding is usually caused by prolonged rainfall. When the soil becomes saturated it cannot hold any more water and rainfall is quickly delivered to the channel leading to higher discharge and floods.
Short duration rainfall events can also result in flooding if they are very intense. The amount of rainfall can exceed the speed at which infiltration into the soil occurs. This is called a ‘flash flood’. Flooding can also be caused by snowmelt.
Recently there has been very bad flooding in the Yorkshire Dales that has damaged buildings, transport routes and crops. This is a result of very high rainfall. Scientists have suggested that the increasing amount and intensity of rainfall is a result of climate change. Other factors can contribute to flooding.
This photo from the Darlington and Stockton Times shows the amount of water at Hawes bridge in December 2015.
Can you explain how each of the following could contribute to flooding?
- Compacted soils