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NOTES APPERTAINING TO DIAGRAMMATIC DRAWING OF GOTE ROAD FLOOD PROTECTION
Geographically the Gote area is probably the lowest lying area in Cockermouth, adjacent to the rivers Cocker and Derwent and has been prone to flooding for many years. Detailed maps of the area dated 1860 show many watercourses in the area of the present allotments, with a structure known as Blackfriars Bridge crossing these streams in a position where the green is presently visible outside 61 Gote Road, other stories tell of a large pond in this area where drovers use to let the cattle drink before entering Cockermouth market, as it is the lowest downstream point on the River Derwent it is not surprising that all water discharges aim for this location, with one fundamental flaw, when the river is in flood many of the discharge pipes cease to work.
It was fairly obvious from the outset that the river was probably the major cause of flooding, (ignoring November 2009 as a one off) for many years the river has come over at this point but in the last 6 years we have had 3 floods, so why all of a sudden is this occurring more frequently, is it?
- Global warning
- Poor river management
- Alterations in pipework associated with the UU pumping station
- Blocked storm water drains
- Bigger demand on the drainage system
- Increase development in the Cockermouth area.
- Poor upper level river management.
All these questions needed addressing before deciding on an action plan, it did however become quickly apparent there were three sources of water creating the problems;
- River flooding
- Surface water flooding
- Rising ground water flooding
HOW TO ADDRESS THESE PROBLEMS
RIVER FLOODING; various ideas were looked at including digging a swale through Broomlands thereby taking the pressure off the Pump House corner of the river, but this would not give a 1:100 year defence; heavy rock armour defence on the river embankment, but this brought up all sorts of environmental and aesthetic issues, so it was narrowed down to what is called a retracted linear defence (an earth embankment and concrete wall in parts) from Gote Bridge to Waterside Cottage, giving a 1.100 year defence with a 300mm freeboard, this is calculated by using previous flood height records and then adding 300mm as a safety buffer.
SURFACE WATER FLOODING; early on in the appraisals it was becoming apparent that the sole issue of flooding was not down to the river alone, to better understand the highway drainage layout drawings were requested from Cumbria County Council, we were informed none were in existence, but Andidrain were in a position to conduct a complete and detailed survey and 3-4 days would be allocated for this project, nearly 2 weeks later the survey was completed, highlighting many totally blocked main drains and much of the trunk sewers network collapsed or broken through old age.
Also highway inspectors thought that the said sewers ran into the adjacent United Utilities pumping chamber and then pumped away, this theory was flawed and it was discovered that the storm water sewers ran directly into the river, that is when the river is low enough to accept the water; in a flood situation the water backs up the pipes and eventually floods the Gote area.
GROUNDWATER, no matter how water enters your house, flooding is flooding after all, residents told stories of water bubbling up through the floors when the river was high. So, we started taking daily readings from Peizometers left in the ground by the Environment Agency, a Peizometer is a small diameter tube set into ground in some cases 10 -15 meters deep to establish the geology and hydrology of the ground, over a period of 6 months it was clearly established that the readings taken exactly matched that of river flow heights, varying from ground level to 1.8 metre below ground level, so therefore when the river was in flood the water was at ground level and started percolating through the floor slab and into the houses. How do we deal with that? the only ground engineering solution was to place French drains (gravel filled trenches with perforated pipes) around the most prone areas i.e to the rear of the defence and in the allotments. The drain down the centre of the road is already acting as a massive land drain, but designs are being worked upon to place a more permanent scheme in Gote Road itself when funds permit.
To add to all the problems each source of water was handled by different organisation; RIVER water by the Environment Agency, SURFACE WATER by Cumbria County Council Highways and GROUNDWATER by a combination of Cumbria County Council and Allerdale Borough Council.
And to add further complications, a new law was passed in the spring called the Flood and Water Management act 2010, which defined who was responsible for what and how they should go about identifying responsibilities, this threw some of the authorities as they had not fully prepared themselves for the introduction of this act.
To construct a substantial earth bund complete with compacted clay core to a predetermined level and stone faced concrete retaining wall within the grounds of Waterside Cottage.
The drawing indicates the various techniques used to overcome all of these problems, the most complex being the construction of a major pumping station, working on the principles that under normal rainfall and river levels the entire Gote Road drainage scheme will work under gravity, only when the river rises to a flood situation and the flap valves situated on the end of each pipeline automatically close, will the piped water build up, fill the overflow chamber which in turn discharges into the pumping chamber; at a pre determined level the twin pumps will activate and discharge the water over the embankment and back into the river.
Many people have said yes but what if there is a major flood in Gote Road, all the water will be trapped by the embankment, not so, as a major draw down structure has been constructed, complete with Penstock Valve one end (a penstock valve in this case is a large gate raised by winding a spindle similar to that found on canal lock gate) at the other end is a large flap valve restricting the river water from entering Gote Road.
ARE WE STILL AT RISK?
Hopefully not, the works have been designed on a 1:100 flood which means the residents should be able to get insurance cover, but once again let’s make it quite clear no defences in the world would have stopped the November 2009 flood, even if the National Grid or local sub station fails, we still have the capacity to couple up a generator and keep the pumps working.
In my opinion the works have been well thought through and have covered all eventualities, with further proposed works scheduled for the town this summer, together with improved highway drainage in Gote Road, the Gote area will no longer be at risk.
Mike Apperley (Civil Engineering Advisor to the Group) tel 01900 825889 dated January 2011
Rest assured residents of Cockermouth, a great deal of work is being undertaken to ensure that all aspects of flooding issues are being listened to and I am pleased to say that the majority are either being constructed or in the stages of design.
For the past year I have read the articles in the Times & Star and noted your concerns, perhaps the only point we have failed on is feedback to the general public, our problems there have been the speed at which developments have been happening, with often changes to design or ownership being rethought at the eleventh hour.
Let me take you through the last 12 months where the Cockermouth Flood Action Group (CFAG) has been working very closely with the Environment Agency. This time last year there were going to be no major defences in the Gote area until at least 2015 (this would now probably read 2020 in the present financial climate), the removal of gravel from within the river was a big “no,no”.
So here we are 12 months on and there is much to report. After a year of meetings (I have attended at least forty technical ones), we have a defence in place to the rear of the Gote, no mean feat in itself, having to deal with Environment Agency, Cumbria County Council, Andidrain, Allerdale Borough Council, Cockermouth Town Council and deal with water coming from three different directions, from the river, from the highways and rising ground water, so as you can visualize nothing has been simple or clear cut.
Lets now deal with the 2009 major flood, we must get it quite clear, no defences in the world would have stopped what happened that day, but what we can try to eliminate is continual flooding bringing misery to the residents of the town. worth noting that over the past ten years devasting flooding has occurred somewhere in the country;
Lewes Oct 2000,
Boscastle Aug 2004,
Carlisle Jan 2005,
Morpeth Sep 2008,
Cockermouth Nov 2009
so you can see there is no rhyme or reason where and when its going to happen next, lets hope it never returns to Cockermouth.
Recent letters to the paper have inferred that given another major flood, the water would be trapped on the landward side of the defence…not so, as a major draindown structure has been constructed to overcome that very problem, that along with a three metre diameter pumping chamber complete with mains driven twin pumps, any water will clear away rapidly should the occasion arise, under normal circumstances the water will run away under gravity.
Then we have the issue of flooding caused by highway drainage, under the old system when the river was in flood the system stopped and the houses flooded, this has all been bypassed with the water
dropping into the pumping chamber; what about ground water? every time the river is in full flood the
land becomes saturated and eventually percolates through the floor of the houses, with french drains
behind the properties and in the road (works hopefully scheduled for 2011) this should lower the groundwater sufficiently to overcome this problem.
What else, well, we started off 10 months ago looking at a swale through Broomlands, but this did not give the required defence levels to satisfy the insurance companies, but it had some benefits, the Cockermouth Flood Action Group is still a firm believer in this scheme but as the funds available would only stretch to either a swale with 1:25 years protection or an embankment behind the Gote giving 1:100, the EA could not advocate spending nearly a million pounds on a scheme that would not adequately defend the area, so we agreed but still remain positive that one year we will see Broomlands being utilized for the flood relief of Cockermouth.
Gravel, aagh!!! that’s what we’ve been waiting to hear you all say, after the rapid removal of the gravel build up from Gote Bridge area last winter, other areas are being investigated for the annual maintenance programme so it’s a case of watch this space.
There still remains some work to be done in Cockermouth to give the added protection to the town that is required, recently CFAG were invited to a meeting to view proposals that are presently being worked upon.
CFAG has worked and will remain working closely with the Environment Agency and have moved mountains, raising in excess of £100,000 to fund a great deal of the works, rewritten the rule book in partnering and most of all enjoyed and appreciated working with the EA particularly when it brings rapid results such as this.
On the ground we are in the process of developing a much more robust warning system, in the event of impending flood, the EA have replaced all their gauging stations which feed data minute by minute on river levels to the control room at Penrith, the Group has access to this information, there is also an automatic telephone warning system to everyone who signs up, giving impending flood data, street flood wardens are being appointed around the town, a flood procedure on the ground will kick in, making sure all the pumps etc. are working correctly, all this to make Cockermouth a safer place to live and work
For those who want a more detailed understanding of the workings, once the contractors have gone in the New Year, I am proposing to conduct a “walkabout” on a Saturday afternoon in early 2011 to explain the Gote Road system in detail, that way you can rest assured and sleep at night, also the group is planning to hold a public meeting to explain and discuss where we are and what the future holds
Watch this space for an advert in the local paper stating a date for a “walkabout” and public meeting.
Civil Engineering Advisor to CFAG