Fluvial Flood Risk

Fluvial flooding with overflowing river

Fluvial flooding usually occurs when significant rainfall falls for an extended period of time. This results in the rivers water level rising to the point where it exceeds capacity and overflows onto surrounding land.

What is the risk in Southampton?

There are a number of classified Main Rivers and ordinary watercourses in the city that contribute to the risk of fluvial flooding.

There are many factors that influence the risk of fluvial flooding. As Southampton is an urban environment the amount of water that enters a river, and speed of which it enters, is much higher than a more natural environment due to a high coverage of impermeable surfaces. Other factors that can influence the risk of flooding include high groundwater levels, tidal ingress and blockages within a river channel which reduce a river's capacity.

Who is responsible for managing the risk?

The responsibility for managing fluvial flood risk in the city is shared between the Environment Agency, Southampton City Council and in some instances, riparian landowners. 
Southampton has a number of classified Main Rivers which are the responsibility of the Environment Agency, these include the River Itchen, River Test, Tanners Brook, Holly Brook, Rolles Brook, Monks Brook and Blighmont Crescent Stream.

  • The Environment Agency manage Main Rivers by carrying out maintenance, improvement or construction work where needed to manage flood risk
  • The Environment Agency has the responsibility to issue flood alerts for any Main River in Southampton

The risk of flooding from ordinary watercourses is the responsibility of Southampton City Council. Ordinary watercourses are classified as small streams, ditches and watercourses that are not Main Rivers.

In some instances, the responsibility for maintaining a watercourse lies with the riparian landowner. If you own a property or land which is adjoining, adjacent or with a watercourse you will be responsible for managing the risk of flooding. As a riparian landowner you have certain rights and responsibilities for a watercourse. 

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, these are explained on the following webpages: