Somerset Levels: Reducing the Risk of Flooding
In early 2014 the Somerset Levels and Moors experienced widespread flooding, particularly within the Parrett and Tone river catchments.
The Environment Agency estimated there were more than 65 million cubic meters of floodwater covering an area of 65 square kilometers. Residents of Northmoor (Moorland, Chadmead and Fordgate) had to leave their homes at the height of the flood and many communities were cut off by floodwater.
As a result of the winter 2013/2014 flooding, there were nearly 50 assets (embankments, pumping stations, sluices, flood gates and coastal flood defenses) across Somerset that needed to be repaired before winter 2014/2015. Some of the these repairs were included in the 20 year flood action plan for the Somerset Levels and Moors developed in March 2014, and also the wider Somerset area.
New and more efficient pumps have been installed by the Environment Agency at some key sites and in some areas permanent defenses have been built to replace temporary ones used previously. The standard of flood protection has been restored at the majority of sites, but the Environment Agency is working through the winter to make defenses more resilient.
New flood defenses
The Environment Agency is building a new permanent defense at Aller Drove to replace the temporary defense installed last winter. The work includes raising the road and installing a new kerb, to help reduce flood risk to properties most at risk at Aller.
After working closely with the community at Westonzoyland, the Environment Agency is building a new permanent defense to replace the temporary defense used last winter. This includes a new sheet piled wall which will help reduce flood risk to properties in Westonzoyland.
The 20-year flood action plan identifies the need to review the effectiveness of dredging and identify locations for further dredging across the Levels and Moors.
The 8km dredge of the Tone and Parrett was completed in October 2014, and a project is underway to identify possible additional locations where dredging is, in future, likely to be a cost effective way of reducing flood risk. This will provide the evidence base to support future decisions on whether or not to dredge these sites as part of the 20 year plan.
Other flood risk management options
Dredging can be a solution for reducing flood risk in the right place; it is just 1 option for flood risk management and is not suitable for all sites. There are many alternative ways of reducing flood risk and some may be more effective than dredging, depending on the characteristics of the watercourses.
Other solutions could include building new banks, setting back banks, improving pumping capacity or additional maintenance including weed control and the removal of blockages.
Assessing the costs of additional dredging
For locations where modelling demonstrates an overall flood risk benefit, the next step is to consider the criteria that will influence the costs of dredging, such as the working method, silt disposal options, and environmental considerations.
A broad assessment of the cost effectiveness of dredging would then be provided, alongside an appraisal of alternative options that could give the same, or better, flood risk benefits.