Building on a floodplain creates impermeable surfaces such as tarmac roads, concrete driveways and slate roof.

Water is transferred quickly to drain and sewers and then into urban river channels.

Much of the water that falls on trees is evaportated or stored temporarily on leaves and branches.

When trees are removed much more water is suddenly availble and transmitted rapidly

In arable farming, soil is left unused and exposed to the elements for periods of time.

This is increased if the land is ploughed up and down steep slopes, as water can flow quickly along the furrows.

Permeable rocks encourage a slow transfer by groundwater flow

Impermeable rocks such as shales and clays encourage water to flow overland and into river channels. This speeds up water flow and makes flooding more likely.

The most obvious rasons for river flooding. Long steady prolonged rainfalll will produce rivers which rise slowly but can flood.

Snowfall in another factor to take into account, rivers fall in the UK as precipitation is often sotred as snow during cold snaps.

However, when temperture warms and that snow melts many days' worth precipitation can end up in rivers and cause flooding.