Localised or flash flooding is usually a result of storm level torrential rain and often results in problems in urban areas. Heavy rainstorms can mean that drainage systems and sewers fill to capacity very quickly and over-top.

Flash flooding can become a big problem if the weather has been very dry for some time before a storm breaks, as the land becomes baked hard and cannot absorb the rain when it comes.

It can then run off the land and lead to flooding.

Flash flooding can be very localised but can do as much damage as flooding from rivers and other watercourses.

Localised flooding can also happen following a period of prolonged rainfall when the ground becomes saturated and cannot absorb any more water so it flows of the land.

Watercourses are often culverted (meaning that previously open channels are diverted through pipes) during the building of new developments to channel water away from or even underneath buildings. These culverts can work well for many years but can also cause flash flooding problems following rainstorms or prolonged rain as culverting dramatically reduces the capacity of a watercourse.

Flash flooding can also be made worse when the capacity of small watercourses or culverts is reduced by blockages of rubbish/fly-tipping.

Rubbish can also travel down watercourses until it reaches culverted sections and block them. To help avoid this riparian owners are encouraged to keep watercourses that run through their land clear of debris that might cause problems further downstream.