OFAS – clarifications and explanations

We’re aware that there are some misapprehensions around about the Oxford Flood Alleviation Scheme (OFAS). The items that follow aim to clarify some of these points. Where necessary we have sought answers from the Environment Agency to be sure our facts are as accurate as possible.  We’ll be adding to these points, so check back.

See also a later post on OFAS and development

And posts on gravel mining: Gravel mining – Be careful what you wish for and An Oxfordshire gravel mine, 2018

#1 Willow Walk

Misapprehension

“The proposed 60 metre bridge over the ‘channel’ in Willow Walk will destroy over one third of the Walk.”

Fact

The new bridge will continue from the existing Willow Walk track, just raised slightly higher, and will span 19 metres.

It is designed to take existing vehicles and future maintenance vehicles. It will meet cycleway and British Horse Society standards and be built for a 100-year life span.

Thirteen individual large trees (12 white willows and one ash) and part of two groups of smaller trees will be felled to install the new bridge over the new channel. Willow Walk is about 400m long and a stretch 170m long will be cleared in the middle of it. Once construction is complete 20 white willows (10 on each side of the path) will be planted to reinstate the avenue of trees.

#2 Monks Causeway

(called North Hinksey Causeway in the planning documents)

Misapprehension

“Monks’ Causeway to the Fishes will be no more.”

Fact

Both the formal public right of way (North Hinksey Causeway or Monks Causeway) and the informal right of way will be maintained near the Fishes pub. New footbridges will be installed on both to allow access across the new channel.

See Planning Statement: 4.3.3 Recreation and public access.

#3 Transport of excavated material

Misapprehension

“100,000 tons of gravel are planned for extraction and removal along the single track entry point for cyclists, pedestrians and cars for the rugby, archery and tennis clubs through North Hinksey Village. At 25 tons a truck that is 8000 journeys there and back.”

Fact

There are no plans to transport gravel or any other excavated material through North Hinksey village.

#4 Seacourt Stream

Misapprehension 

“The Seacourt Stream will be damaged as the new ‘channel’ takes the flow away. It will have the potential to become a weed choked and rat infested ditch running behind gardens and the garden of the Fishes pub.”

OFA Comment

The published map is, unfortunately, unclear. It makes it look as if what’s said above is indeed the case.

Correct version

The existing Seacourt Stream as it runs behind the gardens along North Hinksey Village and behind the Fishes will remain the main channel, there will be no change under normal conditions.

The new channel below Willow Walk is not a new first-stage channel, it is a flood relief channel (sometimes known as a swale) which will only come into play during a flood: thus it acts exactly like a second-stage channel for the Seacourt Stream but at a distance from it. The swale is raised compared to the Seacourt Stream so water will only enter the swale when levels get high in a flood. 

The Bulstake Stream is higher than the new swale, so there will be some back-flow from that stream into the swale, reaching about as far as Willow Walk (depending on conditions).

Sketch map to follow.

#5 Trees along North Hinksey Lane

“The Botley Road warehouses were allowed because of the tree cover to the view from North Hinksey Lane. These trees will now be removed.”

OFA Comment

We don’t know the planning history so can’t comment on that. 

As far as the present scheme is concerned it is true that the trees on the left bank (i.e. left as you go downstream) of Seacourt Stream in Hinksey Meadow would be removed – that’s in order to take as little of that meadow, with its special MG4 grassland, as possible, while still allowing a two-stage channel for flood relief. There’s been a lot of discussion about this and it seems the best compromise.

On the other hand the trees on the right bank of Seacourt Stream, beside North Hinksey Lane, will not be removed. 

In addition, new trees will be planted along the field boundary by the warehouses – and in the old paddock by the stone arch bridge on Willow Walk.

#6 Dredging 

“Please dredge and clear the rivers and streams which have not been dredged for 40 years”

OFA comment

Whilst dredging can be of some small benefit during normal flows, a river channel is simply not large enough to contain the high flows associated with extreme floods, even if it has been dredged. Dredging gives the impression that something useful’s being done but the reality is that it’d be largely fruitless here and certainly not enough to significantly reduce flooding from a major flood. Dredging’s not without its downsides either – for example, and not surprisingly, it seriously damages riverine ecosystems, especially when done repeatedly.

Dredging the Thames would not significantly reduce flood risk to Oxford. It’s also worth noting that surveying has shown that the River Thames bed is largely stable. Areas dredged deeper would soon silt up again. 

The low-gradient, slow-flowing, braided watercourses of the Oxford flood plain are particularly prone to silt up again quickly after dredging. Dredging would have to be done frequently to do anything at all and even then it would not answer. If it would we’d be all for it, but it won’t.

There are a few specific locations, mainly associated with bridges and culverts, where local silting does need to be dealt with (see #7 below).

#7 Flood plain outflow

“Please … unblock the outflow from the flood plain by the old Abingdon road”

OFA comment

We have been working for over 10 years to achieve just that. We have had considerable success – a new channel and weir at Towle’s Mill, large new culverts under the railway access road at Redbridge, removal of a redundant level crossing bridge, improvements at Munday’s bridge under the railway in Kennington, and clearance of  blocked culverts under the railway at Coldharbour. Certainly these together must have helped in low level flooding – but more is still needed for bigger floods. Climate change predictions suggest these will be more likely in future. 

OFAS in fact provides just such further measures. As a preliminary, a new culvert was installed (taking advantage of the line being closed anyway) under the mainline railway in 2016 – this will be brought into use as an integral part of OFAS. Still to come, OFAS proposes new large culverts under the southern bypass to pull water through the floodplain; the channel banks of Hinksey Drain will be widened right up to Munday’s bridge to increase capacity, and the channel under the bridge itself will be further cleared.

Together these will greatly improve the outflow from the flood plain.

#8 Trees

“The scheme will destroy up to 4000 trees, a fact hidden by the reference in the proposal to ‘groups of trees’ being removed”

We have consulted the EA on this.

The short answer is that the tree-planting proposal results in more woodland within the scheme after completion than at present.

The long answer is here.

Edit, 6 December 2018: there is now an update on trees and OFAS here.

#9 Two stage channel

Misapprehension

“The two stage channel makes very little difference and there are better options. “

OFA response

Modelling of the scheme, with the two stage channel south of Botley Rd down to Abingdon Rd bridge removed, was undertaken by the EA. This appears as Appendix Q in the planning documents. This shows that without the two stage channel, whilst water levels are reduced from the current conditions they do not reduce as much as with the two stage channel which helps improve flow through the flood plain. Without the two stage channel the levels could still cause flooding in Osney Mead, Osney Island, Earl and Duke St and in the area of offices just west of Seacourt Street (the Minns estate). In the scenario without the two stage channel water levels south of the Devil’s Backbone (footpath to South Hinksey) are lower than with the two stage channel due to the redistribution of flows, with more water passing down the River Thames and increasing flood risk in the New Hinksey area. The alternatives which have been suggested – putting more water into the Seacourt Stream where it leaves the Thames would add water to the area where flooding is happening and would make the situation worse. The option of more culverts under the Botley Rd would potentially help move water from the north side of the road into Hinksey Meadow and would reduce the scale of the channel modifications near the Minns Industrial Estate however this would not be as cost effective as the currently proposed scheme and would not reduce levels downstream of Willow Walk.

OFA believes the two stage channel is required for the scheme to work.

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Annual Public Meeting 2015

Our Annual Public Meeting on 19 November was well attended – we were delighted to welcome many members of the public, local councillors, representatives of all the local flood agencies, an Oxford University researcher and Andrew Smith, MP for Oxford East. Nicola Blackwood, MP for Oxford West and Abingdon, and Rodney Rose, Deputy Leader of Oxfordshire County Council, sent their apologies.

Adrian Porter began the evening by setting out our three key current objectives:

  • support for the proposed multi-partner Oxford Flood Alleviation Scheme (Oxford FAS)
  • maintenance of existing waterways
  • that as and when the Oxford FAS happens, maintenance should be properly provided for from the start.

He went on to give an overview of the past year including our recent boat trip, with the Environment Agency, which identified necessary maintenance on Weirs Mill Stream: this work is being planned and funding being sought. John Mastroddi provided detail on the clearance under Munday’s bridge, which completes the project begun in 2013. Impending planning applications at Seacourt P&R and Oxford Four Pillars Hotel, both firmly in the floodplain, are on our radar.

Nick Hills, our Treasurer, told us that we had £346 in the bank, enough for several years at the present rate of spending! Nevertheless, being the good treasurer he is, he asked people to leave any donations as they left: this raised a very generous £110. Nick set out some of the things we’d been pleased to see in the year: among those not referred to in more detail later on were the permanent pipe under the Botley Road to allow pumping across the road without disruption to traffic (County and City Councils), Waitrose’s use of SUDS at their new shop and the successful public events for OFAS during the summer.

He explained how we support OFAS in principle and are contributing to the process along with the other partners – but always reserving the right to be a ‘critical friend’.

The first of our guest speakers, Joanna Grew from Network Rail, gave an account of their proposed Hinksey Flood Alleviation Scheme: this includes the clearing of culverts at Coldharbour (for which we have been pushing for some time), track raising and installation of new culverts. More detail can be seen in Joanna’s presentation downloadable here. You can download a leaflet about the scheme here.

James Playfair explained the progress of Thames Water’s ongoing sewer survey across Oxford, the Oxford Catchment Study. This is about to enter its second year: already some issues have been resolved including significant improvements to the pumps at Littlemore Pumping Station. The presentation can be downloaded here.

Last but not least Emma Formoy from the Environment Agency gave the meeting an up-to-date account of the Oxford FAS; Emma mentioned the possible wider benefits of the scheme, including for wildlife, and the crucial importance of rigorous modelling. More detail in the presentation downloadable here: this includes dates of the next round of Public Events in January 2016 when a consultation on the route options for the scheme will begin. These can be also seen in the Oxford FAS Newsletter – November 2015, perhaps more easily. In parallel with these events, people will be able to view these proposed options and partake in the consultation online.

Apart from these individual achievements and plans, what is remarkable, and heartening, is the considerable cooperation, for example sharing of modelling data, between these three agencies – i.e. they talk to each other! As one of us commented later, we have come a very long way since 2007. We are grateful to our guests for coming to talk and for all the work their organisations are doing. The sum (assuming they all reach fruition) will give Oxford a better, and more secure and sustainable, future.

Nick Hills presented Steve Smith, Engineer with Oxford City Council, with our Flood Star award for this year. This is in recognition and thanks for Steve’s sterling work on many flood schemes and smaller works over the years, as well as co-ordinating the Oxford Area Flood Partnership.

Peter Rawcliffe spoke about OFA’s suggestion for maintaining Oxford FAS: as this is to be largely a ‘natural’ channel it will be subject to inevitable deterioration – so providing both a problem and an opportunity. OFA proposes that a trust be established, in perpetuity, to manage for both flood alleviation and wildlife. Trustees could be drawn from the several stakeholders – landowners, local authorities, Environment Agency, academics and wildlife bodies – to name just a few. We believe this is a practical way to make the most of what the scheme offers Oxford and its residents and visitors. This 7km channel will be ever more essential to Oxford if climate change develops as predicted. Each km may cost £18 million to build. We need to treasure it: in our view a local trust with local accountability, and autonomy to manage as it sees fit, fits the bill.

Simon Collings discussed modelling: as mentioned above this is absolutely vital to developing the case for OFAS – both to be as sure as humanly possible that it will work and equally importantly that no one downstream will be disadvantaged. We recently attended a meeting at the School of Geography, Oxford University: Simon explained some of the potential pitfalls of modelling that we had learned of there, and suggested that community review of the OFAS modelling (assisted by expert modellers) be included in the scrutiny process. This in addition to review by academic modeller(s) which is already under discussion for the scheme and which we strongly support.

We thank those who attended for their support and we thank our visiting speakers for helping to make the meeting a success. Our thanks too to the West Oxford Democrats Club for generously allowing us to use their hall once again.

More on the work in progress at Munday’s bridge

It looks as if good progress is being made. We’re told the wooden posts will be removed, towards the end of the work.

Munday’s bridge: Network Rail start work to improve the channel

Munday’s bridge under the mainline railway at Kennington is an important route for flood water to leave the west Oxford flood plain. A lot of work was done to improve it in 2013 but the channel itself under the bridge was never properly cut and profiled and large wooden posts were left in situ in the channel. Work started yesterday to put these things right.

Thames Regional Flood & Coastal Committee visit Oxford

The Thames Regional Flood & Coastal Committee (RFCC) met in Oxford yesterday. Following the meeting, members visited sites in Oxford related to OFAS. Members of our steering group were on hand to welcome them and, with staff from the Environment Agency, showed the visitors some of the problems which need to be surmounted to alleviate Oxford’s recurrent flooding.

Flooding which, unchecked, is likely to threaten further the proper functioning, and the reputation, of the city in the future if (as a consensus of scientists predicts) climate change makes extreme weather more common. OFAS offers the only practicable way towards reducing this all too real danger in time.

Work begins at Munday’s

8 April 2013

Work has now begun to improve Munday’s bridge, Kennington. It has been a very long wait (see 9 March) but well worth waiting for. We have been critical of Thames Water recently, over sewer flooding in various parts of Oxford, but on Munday’s we owe them a big thank you, as their work will help not only in Kennington but in the west Oxford flood plain generally. Especial thanks too to the residents who are having to put up with months of work, including pile-driving at night.

Munday’s bridge under the railway at Kennington

9 March 2013

We have been urging that this serious bottleneck near Redbridge be sorted out since 2007. Improvements were made in 2009, but more was needed.

Now there is a multi-partner project between Thames Water, Network Rail, Oxford City Council, Vale of White Horse District Council and Oxfordshire County Council to make further improvements. Delays due to legal issues have now been resolved, thanks to help from Oxford’s two MPs, Nicola Blackwood and Andrew Smith. We hope work will now start in early April, but as things are now almost a year late we will only be sure when it actually begins. Nevertheless, action is in sight, and will help reduce the flood risk for many people.

Pinchpoints

3 January 2013

River levels are still about 1m above normal in the west Oxford floodplain. This emphasises the difficulty water has in getting away from our area. It  has to get under the main-line railway to reach the Thames. There are three bridges under the railway downstream of the Botley Road.

We have been campaigning about the furthest downstream, Munday’s bridge, a 60ft bridge at Kennington, for some years. We are eagerly awaiting the start of a Thames Water project to greatly improve the flow of water under the bridge. There have been delays, but we are optimistic that the work will go ahead reasonably soon. This should reduce flooding of property and the railway line.