Debenham Flood Management Project

Debenham is in the headwaters of the River Deben and a number of tributaries meet in the village.

In most summers the river dries up completely, but heavy rainfall events can cause the village to flood. The most recent flood was in 1993 when approximately 33 properties were recorded as having been flooded. There have been other floods in 1912, 1927, 1936, 1944, 1947, 1956, 1968, 1994 and 1995. The Environment Agency currently carries out maintenance through the village twice a year to remove vegetation from the watercourse.

River through Debenham during typical summer

 

 

 

 

 

The management of flood risk to Debenham is complex due to the three tributaries of the river meeting in the village and the costs of many traditional flood management measures are prohibitive. Thus we are exploring a combination of several different ways to reduce risk, including slowing the rate at which flows enter the river network and getting the water away faster beyond the confluence of the tributaries. Working with landowners and the Essex and Suffolk Rivers Trust, we identified a range of measures which could help reduce flooding in Debenham and also provide water quality and habitat benefits. These are known as Natural Flood Management (NFM) features (such as small flood storage areas and ponds). We incorporated the most promising ten 10 NFM features into a hydraulic model to assess their potential benefits and to ensure that they wouldn’t result in additional flooding to other properties. The model showed that together, the NFM proposals could reduce flood risk in Debenham in smaller more frequent flood events, but that further measures would also be needed. Click here to view the Natural Flood Management Modelling Report.

We are now engaged in detailed discussions with landowners to finalise the size and characteristics of the NFM features and management principles. We will then be seeking consents for some of the features with a view to installing them before next spring.

The larger flood storage reservoirs we have modelled on the Gulls and Derry Brook do significantly reduce water levels in Debenham, however the construction and maintenance costs of these features are much greater than the benefits they provide. The funding provided by the Government is a fixed amount based on the benefits the project provides. As a result, significant funding from other sources (public and private) would be required to progress these features.

Investigations into creating a two-stage channel to help improve the flow of water away from the village are also continuing. Click here to view the Two-Stage Channel Design Concept. This too will require the support of landowners and a local site for disposing the excavated material, however the cost of this work is still likely to be greater than the benefits it provides. Other more conventional options for flood management, such as property level resilience, and improving the flood warning service in the village, are also being considered.

The next phase of work will be to consult more widely with the local community about the proposals and then to develop the preferred options. Funding is available for the current appraisal works and the creation of the natural flood management features, but additional sources of money, beyond flood grant in aid, will be required to deliver any other options.

Sub Group Leads:

Will Todd, Environment Agency - Email: william.todd@environment-agency.gov.uk
Jane Burch, Suffolk County Council - Email: jane.burch@suffolk.gov.uk