Coastal flooding is rated as the second highest risk causing civil emergency in the UK and along with fluvial (river) flooding, it is responsible for £250 million in annual damages.
Coastal flooding is when normally dry, low lying flat land is flooded by sea water. Coastal flooding can occur from a variety of sources. The severity of the flooding can be determined by many factors including the strength, size, speed and direction of the storm. The onshore and offshore topography also plays an important role.
What are the main causes of coastal flooding?
A storm surge is a change in the sea level caused by a storm such as a Hurricane. The main cause of a storm surge is high winds pushing the sea water towards the coast causing it to accumulate there. The low pressure at the centre of the storm also contributes towards storm surges ‘pulling’ the water up. The strong storm winds create large waves on top of the surge which can cause damage to coastal sea defences or breach them adding to flood risk. In some cases there may also be heavy rain increasing the risk of flooding.
Rising Sea Level
According to recent studies, sea levels are rising by around 4mm per year due to climate change, as ice caps melt and the oceans warm and expand. This steady rise in sea level will not necessarily cause coastal flooding directly in the UK as coastline developments and defences are designed to withstand the larger flow of tides. But the rising level gives a higher starting point for storm surges and larger waves that can overtop the coastal defences putting more people at risk of coastal flooding.
Many coastal settlements have developed onto what is known as reclaimed land. This is land that has been gained from the sea due to coastal management or ironically, lowered sea levels. This land, although highly valuable, is low lying and flat, so a small rise in the sea level from a mild storm surge is potentially enough to flood it and cause extensive damage.
A large portion of the UK's population lives along coastlines and with sea levels rising due to changes in climate, the exposure to coastal flooding is likely to increase.
What can I do about coastal flooding?
- Know your risk
- Be prepared
- Have a plan
Sources MET Office, National Geographic