The Somerset Flood Action Plan – Two Years On
By Paul Homewood
Two years on, it is time to see what progress has been made with the Somerset Flood Action Plan.
This is the latest update from the Environment Agency:
The Somerset Levels and Moors lie between the Quantock and Mendip hills in central Somerset.
Much of the area has been historically drained for agricultural and residential purposes. The Levels are cut in 2 by the Polden Hills which run parallel with the Mendip Hills further to the north. The River Parrett drains the southern section and the Rivers Axe and Brue the northern.
The need for improved flood protection
In early 2014 the Somerset Levels and Moors experienced widespread flooding, particularly within the Parrett and Tone river catchments. It is the largest flood event ever known.
The Environment Agency estimated there were more than 65 million cubic metres of floodwater covering an area of 65 square kilometres. 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.
Records of flooding go back as far as the 1600s and some of the more significant events over the last 100 years occurred in 2012, 2000, 1997, 1960 and 1929.
Repairs to flood defences maintained by the Environment Agency
As a result of the winter 2013/2014 flooding, there were nearly 50 assets (embankments, pumping stations, sluices, flood gates and coastal flood defences) 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 defences 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 defences more resilient.
The Environment Agency has contingency plans in place to ensure no communities are at an increased flood risk compared to before the winter of 2013/2014.
New flood defences
The Environment Agency is building a new permanent defence at Aller Drove to replace the temporary defence 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 defence to replace the temporary defence used last winter. This includes a new sheet piled wall which will help reduce flood risk to properties in Westonzoyland.
River Sowy & King’s Sedgemoor Drain enhancement options 2016
The Environment Agency has completed an initial investigation of different options to enhance the capacity of the River Sowy and King’s Sedgemoor Drain. By increasing the capacity of the river system the aim is to reduce the risk, depth and duration of future flooding. The Environment Agency has carried out this assessment on behalf of the Somerset Levels and Moors 20 year flood action plan partners.
A report has been published reviewing the options for a Parrett Barrier to manage flood risk in Bridgwater and the surrounding areas. This review looked at whether the recent flooding, updated data or other evidence might influence the preferred option or timescale for a proposed barrier.
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.
A summary of all the assessments for each of the 10 locations will be published on this website. There are currently no funds allocated for future dredging, but funding partnerships may be able to secure some money for some of this work in future years.
Apart from the temporary repairs, the main actions identified as necessary are threefold:
This has so far concentrated on the Tone and Parrett stretch around Burrowbridge, as the Flood Plan demanded:
The difference between the 1960s and 2014 can be clearly seen on the Telegraph’s image below.
Composite image of the River Parrett in Burrowbridge in the early 1960’s (top left) when dredging was carried out on a regular basis, a recent picture before the current flooding event showing the encroaching river banks (bottom left) and during the recent flooding
While acknowledging that dredging is not the only solution and does not work in all areas, the Environment Agency is clear on the benefits of the dredge so far:
With dredging completed and the temporary pumping in place, fewer houses are predicted by the model to flood if there were to be a repeat of the exceptional weather conditions experienced in 2013/14. If the same exceptional weather conditions reoccurred, flooding would still occur but there would be benefits as follows:
1) significant benefits to Northmoor and Saltmoor;
a. the completed dredging alone would help to reduce the risk of flooding to between 50 and 80 of the 142 properties reported to the Environment Agency as having flooded in 2013/14 in Northmoor and Saltmoor;
b. having additional temporary pumping in place alongside the completed dredging would provide significant additional benefit. It could help to reduce the risk of flooding to nearly 130 of the 142 homes which were affected on these moors in 2013/14 and reduce the time of flooding from the 6-7 weeks experienced in 2013/14 to 1 week for those that are still at risk.
Further potential dredging locations have been identified, particularly the Northmoor Pumping Station to the M5 bridge, but these depend on funding decisions.
2) River Sowy & King’s Sedgemoor Drain enhancement
Below is an extract from the Environment Agency Improvements Plan in December 2014:
Some improvements have been carried out during 2015, and more are planned for this year including channel widening.
Key to the successful operation of the KSD is the pumping system at Dunball. The Somerset Levels are so low that the rivers cannot normally drain to the sea at high tide.
It has therefore been vital to provide a permanent pumping system at Dunball, able to pump water into the estuary at all times.
Since April 2014, the Environment Agency has spent £2.5 million improving pumping infrastructure at Dunball, as well as Saltmoor and Northmoor.
The example of the Somerset Levels shows that there are no simple answers to flooding, and that many factors play a part, including dredging and channel widening.
But key to the new approach has been the creation of the Somerset Rivers Authority, which is run by a Board of partners from the five District Councils, Somerset County Council, the Environment Agency, the Parrett and Axe Brue Internal Drainage Boards, the Wessex Regional Flood & Coastal Committee and Natural England.
The SRA’s purpose, according to its website, is to deliver higher standards of flood protection than would be funded nationally, and to create better flood protection and resilience against further flooding by joint planning and delivery.
In other words, decisions will now be made at a local level, by people who understand the problems and solutions, and with a clear objective in mind of improving flood protection.
There is much work still to do, and the Levels will never be totally free of floods. Nevertheless, locals tell me that the work done so far has prevented any flooding so far in this wet winter.