The existing Bridgwater Tidal Barrier scheme has a flaw.
Water can go around it.
Any system including a flood defence system is only as good as its weakest link. The banks of the River Parrett is the Achilles heal of the EA’s scheme.
The ground along the river is simply too weak to support the continued raising of the river banks and from the EA’s point of view too expensive to maintain. The Parrett’s highest tides hidden behind the raised banks are already at the top of the doors of Bridgwater’s houses along the A38.
Even before it’s been built and the complete scheme revealed to the public the EA is working on adding secondary flood banks (dashed red lines) on the premise of a bank failure or a future decision not to maintain the existing flood defences. The drawing below is a scheme the EA has to fix the flaw. The red arrow is the open back door at Walpol where a breach to the north could circumvent all the defences. When the Dutch build a dyke they don’t build another one a few hundred metres behind it; clearly the EA expects a failure to occur or the river to over top.
The line in green is an option never considered by the EA but one that would offer much better protection than what is being proposed.
This is information never presented to the public in any of the consultations in 2016.
To my knowledge Bridgwater will have the UK’s only tidal surge barrier not located at the mouth of the river it’s meant to control. At Bridgwater’s present rate of expansion the proposed barrier will in 100 years time not be just near the centre of Bridgwater but within the centre of its developed area. Only in Somerset would anyone come up with the plan we have and think its acceptable to have a scheme that has such an obvious flaw. Let’s also not forget that the EA’s other wider site downstream is being reserved for a road bridge to land that the EA is not protecting in the same way as existing housing. What happens when that is to be developed? Start again?
The ratepayer should have had real options presented rather than the EA’s version of the Henry Ford motto “any colour you like as long as its black”, ie anywhere in the river as long as its at the narrowest part of the river we can persuade people to accept.
The letter below confirms that the barrier can be circumvented.
I am currently in Shetland overseeing the rebuilding of some badly built concrete and reporting on the causes. One of the primary reasons for the situation is the multiplicity of organisations in the delivery process where people in those organisations chose to assume the “other people” whoever they were had looked at it and checked it.
The result was that a completely avoidable problem occurred. The details of the incident do not matter what does matter is the lack of knowledge and responsibility in the delivery chain. People assumed and did not have the experience to put their hand up or were overruled on issues that were clearly obvious if people followed normal practice.
The UK is seeing increasing local control of significant long term infrastructure development passing into the hands of local councillors who have no access to independent advice. The low level of scrutiny and lack of third party review now being applied to tax payers expenditure is of great concern. LEP funding organisations seem equally poorly equipped accepting what the EA, Highways and other statutory bodies choose to tell them.
In 2016 I provided written evidence to the House of Commons
Environment, Food and Rural Affairs Committee Second Report of Session 2016–17. The concern being that important infrastructure projects being locally run did not have adequate over sight. Once local authorities had the District Engineer whilst central Government oversight is at such a high level and based in London that it is largely irrelevant to the population. We have no competent independent oversight on the many state funded projects taking place regionally.
Recent correspondence with The Somerset Rivers Authority indicates that organisation has all the indicators of an organisation with inadequate resources and a scrutiny committees that appears to have no terms of reference and no access to third party advice. No large commercial organisation would operate in this fashion. It is noteworthy that the EA in response to recent questions describe themselves as a subcontractor to the SRA.
There is little doubt that there is some huge embarrassing and expensive mistake on the way. It is time the regions had independent Engineers who can advise our councillors and has the power to bring statutory organisations to the table. Someone who lives in the region who can drive solutions to the tax payers benefit rather than the continuing creation of separate infrastructure rather than integrated solutions.
As usual we have too many people in positions of influence who don’t know what they are talking about and consultants more concerned with fee income than doing the right thing. Bridges on Tidal Barriers for instance.
If the regions want independence they will need the tools to do the work. Our infrastructure delivery needs to better managed and supervised.
In November 2011 a section of Bridgwater’s West Quay collapsed. It was an old quay wall, possibly medieval in parts and close to or at the location where the demolished Bridgwater Castle would gain access to the River Parrett. Whilst there is no official report explaining the failure it was probably the usual one; a build up of water behind the wall that exceeded the ability of the wall to resist it. It had rained very heavily beforehand. This is why holes are provided at the base of retaining walls to let the water escape and reduce the water pressure behind. Old walls often fall over and some relatively new ones fall over as well.
However since collapse the EA and Sedgemoor District Council appears to have developed their own interpretation on the collapse implying that West Quay is a flood defence which it isn’t. It was part of the old port of Bridgwater and the legacy of that commercial activity.
The EA’s public 1016 consultation boards on the Bridgwater Tidal Barrier imply that the West Quay collapse would not have happened if the Tidal Surge Barrier and its associated defences had been in place which is implausible to say the least. It also makes a statement that the wall was in poor condition, who knows what condition it was in and a wall can be in perfect condition and still fall over if its capacity is exceeded.
Sedgemoor ratepayer’s have been asked for comments on the location of the the Bridgwater Tidal Barrier in 2016 and the Draft Local Plan in 2017. They rely on the efficacy of the information provided by our statutory authorities and in the case of West Quay the information and the story presented seems questionable.
One of the problems with building the Bridgwater Tidal Barrier downstream of Dunball Wharf is the marine traffic to Dunball Wharf. Sedgemoor District Councils current draft local plan states “The Council will support the continued operation and potential development of Bridgwater Port including Dunball Wharf and Combwich Wharf (Policy D16 applies). It will also support the re-establishment of active commercial wharf’s at suitable locations elsewhere on the River Parrett. In all cases the construction or operation of new wharf’s should not adversely impact upon the Severn Estuary internationally designated site.”
The reality is that the Dunball Wharf’s with their tidal drying berths, dependency on high tides and difficult navigation is never going to be a commercial success but the 200m wide river at Combwich might. Construction of the tidal surge barrier could enable the relocation of Dunball Wharf to a better location.
Much hangs on what is considered to be adverse.
Concepts of what the river structures might look like have not been forthcoming since 2009. Apart from the tower and turning vertical gate Bridgwater’s gate structure will be considerably shorter than the Hull Barrier structure we have been repeatedly shown.
What would a barrier with a road bridge options look like?
Another wharf at Combwich, EDF have one there already, would not require an opening bridge or clearance much more than Drove Bridge on the NDR. A tidal surge barrier with a 40m fixed navigation span and a road deck might look like
Keeping Dunball Wharf would require a one larger gate and an opening bridge. Dunball currently sees 40 or so vessel movements a year so its operation would not affect the bypass traffic.
The engineering is relatively simple and with a purpose built wharf everything could be shipped in during construction.
Bridgwater’s has had a long running debate over the type of gate for the proposed tidal barrier. Bridgwater Town Council and the Inland Waterways were led to believe that only a rising sector gate, similar to the Thames Barrier, could deliver the penned solution which they want in order to maintain the water level in the river and that would be delivered. As an an attendee to the September consultation the message of a rising sector was firmly reinforced to the public when a video of a rising sector gate was continuously shown at the now selected site and various supporting images included on the static displays.
The rising sector gate aka Thames Barrier was always a red herring and never going to be built. Only a barrier downstream of Dunball where the Hanson dredgers transit to Dunball might have supported an argument for it.
Regardless of the merits of Penning the River Parrett the point made by the EA that penning could be incorporated at a later date is well made. To illustrate how that might be achieved can be seen below
Once the planned barrier has been built it would not be difficult to do this if it was wanted.
What is more concerning is that after 2 years of presentations people deeply involved in reviewing the scheme still do not understand it. That they feel they were led to believe a rising sector gate would be provided is completely understandable. It is also something that despite the issue being closed in November 2014 the EA have chose to keep open until now. References to The Thames Barrier, Boston and Ipswich were at best inappropriate. The Thames Barrier actually consists of a number of other vertical gate such as Barking Barrier, Dartford Barrier as well as the more famous one.
Does the gate type actually matter? No.
It is a lesson to those presenting options to the public and our representatives.