Dear M
Not sure your article content in last Fridays Cumberland News sufficiently presented our preceding telephone interview responses. It would be helpful to Carlisle Residents if the points I made, summarised below, could be included in a follow-up article so that the CFLAG position is clear–
· The Environment Agency proposals have back tracked and become limited to defence wall up-lifting (200mm not the 2mm stated in the article).
· The Eden river will be carrying 2 million cubic metres of additional water in a Desmond equivalent event as at least this amount escaped past the existing defences so peak levels will be higher without other river management techniques being employed and we are worried this has not been sufficiently factored in.
· Carlisle Flood Action group (CFLAG) is concerned that ‘conveyance’ of the Eden river water will not be aided by leaving the Eden bridges arches compromised by gravels and sand banks and spit deposit material up and down stream which can only keep flood peak levels higher (because volumes in conveyance have not been optimised through the arches early in a flood event).
· River bank ‘smoothing’ to aid conveyance flow rates could play a much larger part than in the proposals.
· There is real commercial concern that the Eden bridge itself (a gravity stone structure in two halves) cannot accept Despond scale flows without risk of damage. Another Desmond without encouraging lower peak levels will inevitably close the bridge as a precaution seriously hampering movement between the north and south of the City.
Regards
John L. Kelsall
BArch, Dip Arch, MA, RIBA, MRTPI, FRSA
Chair – Carlisle Flood Action Group
12 August 2020 12:12
Thank you for your detailed reply Colin which CFLAG, with your permission would like to include on its blog page for wider viewing.
There is little new here but it is extremely helpful to have current clarity on the local EA perspective. You would be surprised, I’m sure, if I did not offer a measure of repost –
We at CFLAG (and also via the county CRAGG) have argued from 2015 that flood risk management should comprise the application of all ‘tools in the box’ in a timely and appropriate way. The avoidance/reduction of flooding can be achieved with the aggregation of many small positive incremental steps, indeed, we have agreed from our earliest meetings with your team that there is no ‘silver bullet’.
REMOVING GRAVELS
The management of in-channel and bank/floodplain gravels and transit sediment is a corner stone to FRM. It is not a binary issue – to do or not to do once only – it is a matter of annual maintenance. Of course once cleared the problem areas will be replenished by the river – this is the way it has always been and I don’t think anyone that we have spoken to suggests a one-off dig would have lasting benefit which is what your reply implies. The recent Salford University research on the river Caldew proves there is latent deposits within major rivers annually accruing from the surplus of erosion into the river and over the volume exiting through the system. This excess used to be extracted via a regular maintenance programme through a system of suitably located catchpits which we understand ceased to be emptied not long after the transfer of assets from the NRA to the EA. It is a national major issue to be resolved and it recurs in local advice wherever there has been a damaging flood. This is not accidental or coincidence it is a recurring call to reverse a damaging national EA policy recognised across the spectrum of affected communities. Although in the case of Eden bridge (and it will apply at many other locations) the benefits may be considered minor – if it is not done it is a dis-benefit which will continue to get worse meaning other works have to be more efficient to win back even further protection to get to the same place and even then it will not be enough - a very clear example of how the funding calculator is in error as it tries to compare ‘capital’ cost benefit with what should really be on the ‘revenue’ side of the budget ie. Maintenance not project. We have gone blue all over trying to press this point which keeps getting deflected and in that we appear to share the views of Mark Worsfold (Infrastructure UK report on EA operations 2014) which was considered by the Govt. Environment Audit Committee with recommendations that the EA appear yet to have set in place particularly in reference to the maintenance of assets. It is appreciated that this aspect is above your level of local control but it is where you should be pushing, and vigorously, internally.
DEFENCE WALLS
Defence walls should be regarded as contingency second line protection. It is the ‘tool’ of last resort as any failure or mis-calculation (I cite Melbourne Park and the Sands Centre 2005 -2015) has catastrophic consequences. Total reliance on walled defences – which is what the Carlisle project appears to have become – is a financial expedient too far and ‘Flood Risk’ has not been significantly reduced so I would disagree with your view that increasing the wall heights offers greater benefit per £ as the risk element of a matrix remains high. A river managed to a lower peak may cost more but offers greater risk reduction per £. If the EA can deflect conveyance improvements to the future to counteract climate change surely this can be seen as an available benefit now. Walls are the simplest solution to meet of needs of any modelling algorithm but they are not the best.
CONVEYANCE IMPROVEMENTS
Given that the majority of riparian ownership through Carlisle is vested with public bodies I find a reluctance to engage with this valuable ‘tool’ quite astonishing. Carlisle City Council (in the main), the County Council/central Govt. (schools etc) and Network rail (public operator) must surely have been engaged with you on this matter – have they refused to play their part? If so I believe the citizens of Carlisle need to be informed to make their feelings heard as it seems that potentially very useful works in the public interest are not being progressed to smooth flows through the City.
PHASE 3
We have been advised on a number of occasions at the outset that Phase 3 would include improvements in the vicinity of the West Coast Mainline bridge as this is acknowledged as a particular throttle point (evidence- degree of white water during Desmond) and that these improvement would be instrumental in releasing the benefits built into Phases 1 and 2 ie by improving conveyance in releasing obstruction and thereby lowering the river peak. It appears the necessary improvements are out of EA hands and in the control of Network Rail with no time line or surety. An impasse can be seen in prospect with the Rail Act –v- the Environment Act compromising a flood friendly solution on infrastructure finance grounds.
It appears to us that Phase 3 is likely to offer little prospect of increasing conveyance without improvements to the viaduct and that as a consequence the conveyance improvements that could have been integral with Phases 1 and 2 have been abandoned for a simple higher level of containment. We do not believe that this is what many would believe to represent Flood Risk Management only physical protection retaining latent risk.
Regards
John L. Kelsall
Good morning John, 12 August 2020 08:44
Thank you for your email it is helpful for us to hear the feedback that you are getting through other channels. I have responded to your questions below and hopefully this will help you explain the situation to the residents that you have been speaking to. If you need anything further from us to support you in these conversations please let me know.
Removing gravel from the channel, with a view to improving conveyance under Eden Bridge, would provide a slight benefit in terms of flood risk. Our analysis, which we think is supported by evidence collected during and immediately following Storm Desmond, shows that the benefit is very minor. We have tried to explain this within the FAQs section of the Carlisle Phase 2 pages on the Flood Hub. Furthermore, one of the issues with removing gravel that has been deposited by the river is that the benefit is only temporary. Gravel is deposited in these locations because there is insufficient energy in the river at this point to convey the gravels further downstream. This situation is unlikely to change and it is reasonable to expect gravel that is removed to be replenished by the river over time. This would also mean that the flood risk benefit would diminish over time and the exercise would, at some point, need to be repeated in order to recover the benefit (for which further funding would need to be sought).
There are often many ways of reducing flood risk to a town or city and the main purpose of our appraisal work is to identify which of these can provide the greatest reduction in risk for the money invested. In the case of Carlisle, we believe that the benefits of raising the flood defences upstream of the Sands Centre will have a greater benefit in terms of reduced flood risk than excavating river gravels from the channel. We also have much more confidence in the way this benefit will be sustained over time.
You also raise the question of wider conveyance improvements works along the River Eden through Carlisle. You are correct that there are a number of ways that conveyance could be improved along the existing river corridor and this would also reduce flood risk in the city by lowering peak water levels in the river. However, it is unlikely that these measures alone could provide the Storm Desmond level of protection that we are seeking to deliver. Each of these conveyance improvement options also have their own challenges associated with them, often involving third party assets, which could take longer to resolve. We believe that the options being proposed by the Environment Agency throughout the City represent the most efficient way of using the money allocated to Carlisle following Storm Desmond to provide the desired standard of protection.
It is probably unlikely that we would receive further funding in the future to raise the flood defences in Carlisle again. So, as our climate changes the standard of protection provided by these structures will slowly reduce. We see the option of trying to increase conveyance within the channel as being one of a range of opportunities to mitigate the effects of climate change and would hope to be able to work with our partners to realise these benefits as opportunities occur.
A good example of this is the work that we are doing at the moment in collaboration with Network Rail. By working with them throughout the planning of their maintenance works on the Eden Viaduct (the West Coast Main Line crossing); both organisations are hoping to identify design solutions which not only meet Network Rails requirements but also improve the conveyance capacity of the structure. This work is ongoing at the moment and we have shared the hydraulic modelling that we have developed with Network Rail to help with this process. This work does not form part of our planned phase 3 scheme as we cannot currently provide the certainty that our business case requires. What this does mean though is that any conveyance improvements at the structure which can be achieved will be in addition to those provided by the Carlisle Flood Risk Management Scheme. Furthermore, the analysis that we have undertaken indicates that improving the conveyance at the Eden Viaduct will not reduce water levels as far upstream as Eden Bridge, so delivery of this would not affect the decisions we have made regarding the nature of the Phase 2 works.
Kind regards,
Colin
Hi Pete 05 August 2020 17:21
Thank you for the feedback. The numbers of those interested is not a surprise.
The only thing we are hearing (apart from the longstanding concern that the Sands Centre should not have been developed on the flood plain) is amazement that the opportunity is not being taken to open the arches and clear the channel of gravel banks/obstructions and the smoothing of the banks to maximise flow rates.
Richard and I also remain very sceptical that a gravity bridge with large parts older than 200 years can be relied upon to take Desmond peak rates +. The consequences of getting this wrong will be commercially catastrophic let alone the high potential for loss of life if the bridge is not closed in time (nb. Last time when the bridge was closed by the flood there were many sight seers on the bridge before the police put in a barrier).
If, as we have been told, the gravel and bank work at this major pinch point will have negative effect because the up and down stream flows balance then are you not pre judging that Phase 3 work which should free conveyance to the west will also not be effective (ie physically defend only)? If Phase 3 improves conveyance ie via improvements such as at the West Coast rail line bridge then the Eden Bridge work increases in merit and value yet it will have already been passed over by being discounted within Phase 2. It seems to us that there is little in the way of improvements to conveyance management or co-ordination of river peak timing in the project generally only bank and wall containment (the Petteril on Melbourne Park) and flood wall raising (Eden adj Hardwicke Circus etc).
We, and I am sure many others, are disillusioned that the works outlined at the public liaison events are not fully coming to fruition. Remember if we have another Desmond the defences and infrastructure will have to cope with the damaging extreme peaks as before plus the extra 2 million cubic meters that escaped passed the defences which caused such misery – a seriously large ask indeed.
Regards
John
Hi John, Richard 05 August 2020 16:4
I have just been told by Newground that since the Ph2 page went live at midday on Friday on FloodHub we have had 492 views of the Carlisle Ph2 page. Unsure if any of those are “repeat” visits but sounds really positive in terms of people being able to access the information. I’d expect it to grow with Volkers presence on site today to start pre works and compound set up, so it would be great to hear any feedback you’re getting from residents and for you to signpost any questions you receive to this resource.
