Tidal Flood Risk

Image of Southampton water

Tidal flooding is the temporary inundation of coastal areas during exceptionally high tides or storm surges. This type of flooding usually occurs over a short period of time across high tide however, it can quickly cause significant impacts to low lying coastal areas.

Tidal flood risk is increased when a number of factors coincide, these can include:

  • Spring (high) tides
  • Strong coastal winds
  • High river levels (tidal locking effect)
  • Low atmospheric pressure
  • Significantly high rainfall

What is the risk in Southampton?

Tidal flooding is the greatest flood risk facing the city with approximately 10% of the city being identified as at risk. As the effects of climate change are realised, the amount of properties and businesses at risk is likely to increase.

Currently, there are no formal raised flood defences in the city, and where defences do exist they are in private ownership and offer varying degrees of protection. However, Southampton City Council in partnership with the Environment Agency is in the initial stages of developing a flood infrastructure scheme known as the River Itchen Flood Alleviation Scheme which aims to reduce the risk of tidal flooding to large areas of Northam, St Marys and Chapel.

Who is responsible for managing the risk?

The Environment Agency has a strategic overview of all sources of flood risk which means they coordinate various high level flood risk management activities across the county. As part of this, the Environment Agency is responsible for the management of tidal flood risk including the implementation of flood risk management activities such as maintenance (excluding privately owned assets) and building of flood defence assets.

How can you prepare?

There are many steps you can take to both reduce your risk of flooding and to keep yourself safe in the event of a flood.