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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OFAS: Environmental meeting

OFA attended a briefing yesterday (22 May 2018) on the Environmental Statement which forms part of the OFAS planning application. This was organised by the Environment Agency (EA) specifically for local environmental groups. Penny Burt, Phil Marsh and Graham Scholey for the EA covered different aspects of the scheme, and provided updates on the various environmental assessments being conducted.

The scheme will result in the creation of a continuous area of marshy meadow either side of the new channel with various scrapes and ponds to enhance the habitat value. Overall biodiversity should be improved and strengthened.

But there are downsides. Rich grassland meadow in some areas will be lost, and while there are plans to create more of this habitat elsewhere in the scheme this is not without risk. Trees will be lost in some areas, though compensated for elsewhere. Some views will change significantly, e.g. along Willow Walk, and at Kendal Copse just north of Kennington.

Several useful comments were made by participants in the meeting about ways to enhance environmental benefits from the scheme which the EA will think about.

Ongoing effective management of the project will be critical and the Environment Agency is now exploring detailed proposals around this with various local wildlife organisations. OFA welcomes the idea of collaboration between the EA and local bodies, but is arguing that whatever arrangements are set up there needs to be a mechanism of accountability to the public, so that local interested parties can understand what is being undertaken, and what achieved – both for flood relief and for wildlife.

 

Flood scheme and bridges

There’s an article in the Oxford Mail on the new bridges proposed as part of the Oxford Flood Alleviation Scheme at Willow Walk and North Hinksey Causeway. We agree with the Oxford Preservation Trust that it’s very important to get these right – with materials and design appropriate for these much-loved and ancient settings.

Note too that Oxford Preservation Trust is hosting a meeting to discuss plans for the channel at The Fishes, North Hinksey, on Thursday, May 31, from 6.30pm to 8pm. At least one of us plans to be there.

An exciting time!

20 January 2011

This is an exciting time!

Things in the Botley Road area which we have promoted and campaigned for for a long time are coming to fruition. The works will reduce flooding of properties by surface water. They result from cooperation between various bodies, including OFA.
At the end of 2008 we suggested setting up an inter-agency working party to concentrate on the Botley Road area. This was immediately taken up by the EA and agreed by the Oxford Area Flood Partnership in January 2009. Things began to move. Oxford City came up with the suggestion of a road hump at the top of Earl Street to redirect flood water; which fitted well with our suggestion that flood water be directed down Lamarsh Road instead of Earl Street, by lowering part of Lamarsh Road. The Earl Street hump is now going in – the result of work by County, City, EA and ourselves.

Very soon we expect work to start in Lamarsh Road, to lower the far end of the road. Here, as well as those already mentioned, developer Kingerlee has played a key role. A new flood route will in due course take floodwater away through the Kingerlee site to the flood meadows beyond.

Not far away, work is starting on another OFA-initiated project: the installation of flood culverts under Willow Walk. Much of the assessment and planning has been done by Oxford City in conjunction with the EA.

New culverts under Willow Walk, North Hinksey

16 December 2010

Oxford City and the Environment Agency have worked together towards getting new flood culverts installed here. We have now heard that work is expected to start around 10 January 2011 (weather permitting).

This should help keep flood water moving, not allowing it to build up so badly.

It is something we suggested and have pressed for for some time. Thank you EA and City.

OFA’s Annual Public Meeting, 2010

25 November 2010

Our third Annual Public Meeting was held at the West Oxford Democrats Club, Osney Island today.

Very many thanks to the Club for once again providing us with a warm and comfortable venue – not to mention the bar!

The meeting was attended by over 80 people. We had had some concern that numbers might be down as it is now 3 years since a major Oxford flood, but thanks to Andy Webber’s efforts in distributing flyers, that did not happen. A big thank you to everyone who came out on a very cold night.

It was good to see Andrew Smith, MP for Oxford East, who represents many flooded people along the Abingdon Road and elsewhere. He had with him a copy of our Building on Success, and has asked us to keep him in the picture about things at Redbridge, which affect his constituents as well as those further west. We are delighted that he said he will support us in getting necessary flood risk reduction work done there.

Flooded people from many parts of Oxford were present as were City and County Councillors and officers from City and Environment Agency. Among them it was good to see our previous Flood Stars, Nigel Bray (EA), Susanna Pressel (City and County Councillor) as well as Mary Timbrell (resident of Duke Street).
Andrew Smith MP (L) and Barry Russell, EA

Andrew Smith, MP for Oxford East (left) and Barry Russell, Area Flood Risk Manager, Environment Agency, at OFA’s APM.

keith andy flood star 2010 APM_2

Keith Hutchence (R) of the Environment Agency was awarded our Flood Star for 2010. He was thanked for all he has done and presented with a unique bottle of “OFA Flood Star 2010” by Andy Webber.

Presentation by the EA
We were pleased to be sharing our meeting with the EA. They have been thinking about further ways to protect the Earl and Duke Street and Marlborough Court area, in particular possible ways of keeping water out of the back of properties bordering the Bulstake Stream. Barry Russell, EA Area Flood Risk Manager, presented these ideas to the meeting and answered questions. The ideas are at an early stage and residents will be consulted further; any comments in the meantime can be made direct to the EA or via your local OFA person.
Barry told the meeting about the planned pavement hump for the Botley Road end of Earl Street, which will be topped with a row of sandbags during flooding, keeping water out of the street. The County Council will be installing this in the New Year. There are also plans to provide a removable flood barrier for the alleyway into Duke Street from the east, to stop water flowing into the street from the Bulstake Stream.

Peter Rawcliffe then spoke about:

Events and work completed in 2010
January: Network Rail remove redundant level crossing bridge at Redbridge.

March: publication and launch meeting of our Building on Success, Suggestions for medium-term measures to further reduce the risk of flooding in Oxford and the surrounding area. See list of attendees at the launch meeting here.

EA clear Hinksey Stream from North Hinksey to Redbridge.

November: meeting with EA’s Director of Operations; Head of Operations; and Thames Regional Director, and others.

Maintaining and developing our website.

Still in progress, but now heading for a successful conclusion:

  • Duke and Earl Street – see above.
  • Lamarsh Road as a flood route, to which we have made an important contribution – initiating the idea (March 2010), pressing the case and helping with the assessment (Oct 2010). The City, County, EA and developers Kingerlee have all played active roles and we are together on course to a successful conclusion. The result will:
    • Benefit existing and new businesses in and off Lamarsh Road.
    • Benefit residents who reach their houses via Lamarsh Road – Oriel Mews, and in future Rewley Press and Kingerlee housing.
    • Divert water away from proposed Earl Street pedestrian hump. The level in Lamarsh will be just lower than the height of the hump plus one sandbag.

2011: in the pipeline already:

  • Willow Walk, North Hinksey – culverts are to be installed to move water more quickly down the floodplain. Suggested by OFA and taken up by  EA and City.
  • Hinksey Stream, further clearance at Redbridge (EA).
  • Network Rail, clearing several waterways and renewing weir north of Redbridge.
  • Lamarsh Road – see above.
  • Culvert through causeway at South Hinksey (Vale of White Horse).

OFA’s top 4 for action in 2011:

John Mastroddi described the issues at Munday’s and Stroud’s bridges at Redbridge. See Building on Success.

Richard Thurston spoke about two things that would help Osney Island:

  • West Street Pumping Station: upgrade the current pumping station by installing a pump of greater capacity.
    Redesign the outfall so that the water is discharged with the flow of water in Osney Stream.
  • Build a new spur from the Bridge Street extension road drain via the passageway into the Environment Agency’s land, where a new sump be created. From the sump, excess water would be pumped into the weir pool.

obstructions weir sluice castle mill stream

Mike Hamblett showed us the poor state of the weirs and sluices on Castle Mill Stream – the photo speaks for itself.  Castle Mill Stream has potential to carry more water than it does, having relatively high gradients. We suggest these structures be mapped and listed and their condition and operation be examined, as a first step to improving them.

Mike then spoke of the broken down state of about 500 m of the west Thames bank above Tumbling Bay. See Building on Success. Water pours out of the river here when river levels are high, further damaging the bank in the process. We are concerned that this water may make flooding worse in the Botley Road area. The effect of the water leaving the river, compared to what would happen if it did not do so, should be investigated. As the breakdown worsens with each episode, one can expect that before long the entire bank over the 500m length will be affected – that situation should also be looked at. The bank could be repaired fairly easily.

Resilience and insurance

Nick Hills stressed that the time to install flood resilience measures in your house is when work is being done anyway – including of course after a flood. And that people should make sure this happens, not leave it to insurers – they tend to put back what was there before, chipboard floors and carpets included. Ask that the money be made available to you to spend as you see fit – see articles by Peter Rawcliffe and Nick Hills.

Botley Road area – action

Earl Street, Duke Street and Bulstake Close were badly affected by flooding in 2000, 2003 and 2007. In the past year four things have been done (or are about to be done) to help:

1.  Oxfordshire County Council has installed a culvert from the south end of Duke Street onto King George’s Meadow beyond.

2 . The footpath at the bottom of Earl Street has been recontoured to improve the flow of water into the alleyway leading to Duke Street.

3 . Clearance of Osney Ditch and the Bulstake and Seacourt Streams south of the Botley Road in Autumn / Winter 2008 by the EA.

4 . Improvements at Redbridge are due to be carried out in March 2009. This should benefit everyone upstream.

As discussed on the Background page the flooding in these streets is a tricky and complicated problem; there is no quick fix. OFA has put forward a number of suggestions over the past year; getting progress has been slow because of the complexity and interdependence of many factors, the need to deal with several agencies and the scale and cost of some potential remedies.
Setting up a dedicated group would, we hope, help achieve results and so we proposed to the EA and to the Oxford Area Flood Partnership (OAFP) that an Inter-Agency Working Party be set up to consider this area, produce solutions and implement them. This was formally agreed to at an OAFP meeting in January 2009. The first meeting should be held in February or early March 2009. Members of this group will come from the EA, Thames Water, Oxford City Council, Oxfordshire County Council and OFA. Edit: held March 19th 2009.

OFA intends that this should be a main focus for action during 2009. We have a number of ideas which we believe merit consideration:

1.  Installation of a culvert from Earl Street to King George’s  meadow.

2.  Alteration of the drains so that water entering the drains north of the Botley Road does not end up in Duke and Earl Streets as it does at present. Thames Water and Oxford City have already begun to examine this.

3.  Reprofiling the Botley Road so that floodwater which at present flows across it into Earl and Duke Streets no longer does so. Instead it could be routed down Lamarsh Road and on via a (new) culvert through the site owned by Kingerlee and earmarked for development at the southern end. It would have to be certain that the commercial premises in Lamarsh Road would not be put at risk. And the agreement of Kingerlee would be essential.

4  The west bank of the Thames just north of the Botley Road is  low so that water flows out of the river onto the fields in large amounts whenever the river is full. This in turn erodes the banks further. It is not clear where this water then goes but it must be a possibility that it contributes to flooding in Earl and Duke Streets and Bullstake Close. More information is needed.

5  Willow Walk may act as a barrier to the movement of flood water downstream. This needs to be verified and the EA has agreed to see whether it already has relevant floodwater level data. Closely related is the poor state of the ditch along the eastern edge of Oatlands Park, with partial or total obstruction in several places. Alternative routes are already under active consideration by OFA and the City Council. The overall solution may be to reroute the ditch, to provide culverts under Willow Walk, or to do both.

Oxford City proposes to build a wall to protect Bullstake Close. The effect of this on Earl and Duke Streets is not fully clear and we have asked the EA to evaluate this, to ensure no worsening of flooding will result for those streets.