Houses on Flood Plains

Building on flood plains is not seen as a good idea but  that is only the case when you want to build the same style of house that we build everywhere and is already unsuited to our changing climate and increased recurrence of flooding. Governments   have become quite irrational  basis for restricting development on floodplains especially when  fluvial flooding is considered in the same way as one caused by a failure of our tidal flood defences.

Somerset and similar low lying areas are not flood plains in the normal way, there is a enough room to accommodate the odd flood providing our houses are designed for that environment. There is nothing to stop development on land such as the Somerset Levels , the Fens and other low lying areas. We just need the right sort of housing.

Existing  Government legislation uses a very blunt definition to restrict development but it really depends on the flood plain and what your living in which brings to the word vernacular. A misused word used by developers to continue  building a product that suits their cashflow, that planners use because its safe and objectors use because apart from the great crested newt they have reasons to object and would rather put up with more of the same. We have a self fulfilling prophecy.

We cannot continue building wholly inappropriate housing just because it’s what we have become used to, our housing needs to adapt to our weather will be more extreme and flooding a regular occurrence.  Flooding that  in coastal areas is likely to be largely salt water rather than the largely benign floods  caused by precipitation.

Its not good to have  ground floors we need to put our apartments and gardens above the garages to be  safe. This also means that the miserable balconies  that have been provided to date need to increased to a size  that is equivalent to the equally miserable gardens now considered acceptable. The difference between the two is no longer significant.

Big balconies
really useful balcony
Big Garages
a look through the future

West Quay Collapse

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.

EA Barrier Location Consultation March 2016
EA Barrier Consultation September 2016
Sedgemoor Draft Local Plan 2017

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.

 

A Tidal Surge Barrier, A Bridge & Dunball Wharf

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.

 

 

The Great Bridgwater Gate Debate

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

Typical proposed Vertical Gate
Modified Barrier with Penning weir added, gates omitted for clarity.

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.

Bridgwater Tidal Barrier Location

Today the Environment Agency and Sedgemoor District Council confirmed the recommendation to build the Bridgwater Tidal Barrier within the town.

If this is built at this location everyday millions of cubic metres of saltwater will unnecessarily be brought up the river into the town and particularly North East Bridgwater. Ultimately we will get the very flood this is meant to prevent.