The Environment Agency are planning to launch a new free flood warning service in your local area.


The Environment Agency are pleased to be able to offer a new free flood warning service to residents and businesses located in, or near to, an area at risk of flooding from the Horsenden Stream in Princes Risborough.

Flood warnings give people valuable time to prepare for flooding; time that allows people to move themselves, their families, and precious items to safety.

The new flood warning service is an expansion to an existing flood alert service that we already offer to residents and businesses in the local area who are at risk of flooding from rivers.

The new flood warning service is intended to target those properties that are at the most risk of flooding from the Horsenden Stream, however some properties at lower risk are included in the service.

A small area of the parish of Longwick-cum-Ilmer is covered by the new flood warning service. A map of the new flood warning area is attached so you can see the area it covers within the Longwick-cum-Ilmer parish.

We are currently planning to launch the new service on the 24 May 2023.

Residents and businesses in the new flood warning area should be able to register once the new flood warning area has gone live. Therefore, those residents and businesses who would like to register for the new service must do so after the planned launch date, which is currently proposed for the 24 May 2023.If attempts are made to register before this date our systems will not yet include this new flood warning area.

To get the best experience of the new flood warning service, we recommend that residents and businesses that are within the new flood warning area register their details and create a full account by calling Floodline on 0345 988 1188 or visit our website

We also work with mobile network and telephone providers to automatically register people at risk of flooding to the new service. The service is anonymous and free. If residents and businesses have a phone number that is registered to an address in a flood warning area, and they are with a participating mobile network or telephone provider, they may receive a text or phone message explaining that we will contact them when a flood warning is issued. This does not create an account with full details as we are not provided these by the mobile network and telephone providers. We hold phone numbers securely in our flood warning system in line with our privacy notice.

The accuracy of flood warnings improves over time as we gather more data and get a better understanding of how the river reacts to heavy rainfall. As this is a brand-new service there may be a higher than normal occurrence of false alarms initially.

In some circumstances there may be no time to issue a flood warning in advance so it's important to be prepared, know the signs to look out for and stay alert.

It is important for us to verify what happens every time a flood warning is issued to improve the service. To do this, we deploy staff to affected areas to validate flood extents and our warning alarm levels to improve the accuracy of our warnings.

We welcome involvement from the community to improve the service and would encourage residents and businesses to record and report any actual flooding. If this is something that the Parish Council would be able assist with this would be much appreciated.

You can report incidents of flooding from the river in the new flood warning area within the parish of Longwick-cum-Ilmer to our 24-hour incident hotline number which is 0800 80 70 60 or to Floodline on 0345 988 11 88.

You can find more information on flooding on our website at

You can check flood risk online at

Thames Area Flood Resilience Team

Additional Documents

Horsenden Stream FWA.pdf