Another extreme weather event reported by the BBC today:
“At least 13 people have been killed by flash floods in the Aude region of south-western France.
Local authorities say several months’ worth of rain fell in just a few hours overnight …”
“At least 13 people have been killed by flash floods in the Aude region of south-western France.
Local authorities say several months’ worth of rain fell in just a few hours overnight …”
“Communities will want new flood defences after many Welsh rivers burst their banks during Storm Callum, Wales’ environment agency has warned.
Parts of Wales saw the worst flooding for 30 years ….
A 21-year-old man was killed after a landslip and many homes and businesses were flooded as Carmarthenshire, Ceredigion and south Powys bore the brunt of the storm on Friday and over the weekend.”
We’ve been proactive in Oxford so we’re much further ahead – the Oxford Flood Alleviation Scheme is currently being considered for planning approval. Whether the Welsh floods are in part related to climate change would require event attribution analysis to give an estimate of the probability that that is the case. But certainly it’s the sort of event that one would expect with climate change. It’s vital that Oxford’s as ready as it can be.
It’s raining steadily and hard here today, not enough to flood us but, after the severe flooding in Wales, a further reminder of the threat to Oxford.
Many, many houses and businesses, roads and railway were flooded in seven of the years between 2000 and 2014.
With climate change predicting far worse to come, Oxford needs protection.
We’ve had a dry summer, river flows are low and flooding may seem a long way off. But it’s always a threat as this article on the BBC website today, about severe flooding in Wales, reminds one:
Whether this event is due in some part to climate change may be impossible to know for sure, but there is no doubt that extreme weather events are becoming more frequent across the world. Now is the time to prepare Oxford for that future.
The planning application for the Oxford Flood Alleviation Scheme is being scrutinised; if approved Oxford’s flood risk will be reduced. Without it Oxford will remain largely undefended and future generations will rightly ask why something wasn’t done while the opportunity was there.
The post ‘OFAS – clarifications and explanations’, has had new points added to it (now nine).
We’ve just sent this update to our mailing list
Dear OFA contact,
Since our last update at the beginning of April, the Oxford Flood Alleviation Scheme has been progressing through the planning process, and the Environment Agency is waiting for direction from the County Council following a period of public consultation on the plans. It is likely that an updated suite of documents will be published, and made available for public comment, but the EA is expecting to be granted permission later this year. As part of the implementation the EA is expecting to acquire some land under compulsory purchase orders and notices have gone up recently around the project area about this. Construction is expected to begin in 2019 and take three years to complete.
Some of you may be aware that in recent weeks a group called Hinskey and Osney Environment Group has been formed and has been voicing opposition to the scheme. Much of their case is based on misunderstandings of what is actually being proposed, and we are engaged in trying to correct these misapprehensions, including talking with some of the people involved in HOEG – see https://oxfordfloodalliance.org.uk/2018/09/28/ofas-clarifications-and-explanations/ for more detail.
The creation of the scheme will involve disruption, trees will be removed (but then replanted, with a net gain across the scheme) and the appearance of the landscape will be a little different after the scheme is complete. We understand why this causes concern, but the EA assure us they will be making every effort to minimise the impact.
We’ve spent a lot of time working on options over the years there is in our view no effective alternative to the two stage channel proposed by the EA. This is a fairly ‘natural’ scheme – very far from a concrete channel. This fits well with our vision that OFAS should create a scheme which becomes a haven for nature, where biodiversity is increased. This is something OFA has pushed for and contributed to developing, and which we believe in very strongly. For example, the plans include new features such as scrapes and ponds, and the gradual slope of the second stage channel adds a hydrological gradient – meaning new and varied wildlife habitats. And it’s proposed that the day-to-day management work (at least on those areas owned by the EA) will be by local environmental organisations familiar with managing land for nature, contracted to the EA. We’re looking forward to the scheme area becoming much richer in wildlife than it is now, an asset the city can be proud of and that people can enjoy.
Some people appear to be concerned that the building of OFAS will result in more development in the floodplain. We don’t believe this will happen. The floodplain will still flood, even with OFAS, and in our view the existence of a managed, environmentally rich, scheme, with much of the land owned by the EA, will actually reduce the risk of further development.
The other major issue we’ve been working on, apart from OFAS, is the Seacourt Park & Ride extension. We had a meeting with the City Council at which we were able to obtain details of the design of the sustainable drainage system for the car park. This allayed our concerns about displacement of groundwater, but we remain concerned about the way compensation for displacement of floodwater by the extension is planned. We have asked the EA to explain the science on which their ‘no objection’ was based, and we’ve asked them to identify the professional advice on which they rely. The EA seems to be struggling to provide an answer to these simple questions, and we’re still waiting for a satisfactory response. Our view currently is that the extension of the P&R, in the manner proposed, would reduce flood storage capacity in the floodplain.
We will be presenting at the annual Oxford Area Flood Partnership meeting at Oxford Town Hall on 2 October, 6-8pm. There will also be presentations from the EA, local councils and Thames Water on what’s been happening in the city to reduce flood risk over the past year. Please come along.
OFA will hold its next public meeting in the spring. Further details will follow in due course.
OFA Steering Group.
To be added to (or removed from) our email list go to our Contacts page.
“The proposed 60 metre bridge over the ‘channel’ in Willow Walk will destroy over one third of the Walk.”
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.
“Monks’ Causeway to the Fishes will be no more.”
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.
“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.”
There are no plans to transport gravel or any other excavated material through North Hinksey village.
“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.”
The published map is, unfortunately, unclear. It makes it look as if what’s said above is indeed the case.
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.
“The Botley Road warehouses were allowed because of the tree cover to the view from North Hinksey Lane. These trees will now be removed.”
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.
“Please dredge and clear the rivers and streams which have not been dredged for 40 years”
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).
“Please … unblock the outflow from the flood plain by the old Abingdon road”
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.
“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.
“The two stage channel makes very little difference and there are better options. “
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.
Here’s the full answer from the EA:
Overall the scheme will need to remove around 300 individual trees and 57 groups of trees. The partial removal of a further 44 tree groups will also be required.
We don’t recognise where the figure of ‘4000 trees’ has come from. The reason we talk in terms of “groups” of trees, is because we carried out the trees survey and impact assessment work in line with the British Standard for this type of work. This instructs to use the term “group” specifically to identify trees that form a cohesive feature – such as a group that together provide shelter, or together provide a visible screen. The term “individual trees” is only used for trees that are surveyed as being particularly large. So these terms ‘individual’ and ‘group’ are the required way of classifying trees for assessment.
We don’t currently have specific numbers for trees to be felled and planted, but what we can say is that the tree-planting proposal results in more woodland within the scheme after completion than at present. This will include species that are found locally, such as oak, alder, willow, field maple, hawthorn, blackthorn and wild privet. These woodland areas will be managed for wildlife and include glades that are sown with wildflowers to encourage butterflies and other insects, as well as birds and foraging bats.
We have designed the scheme to keep tree loss to a minimum and once a contractor has been appointed we will work with them to see where we can further minimise losses wherever possible.
Work begins soon on Seacourt P&R extension, which we opposed fiercely.
Members of OFA steering group, along with Councillor Colin Cook, and Stephanie Ouzman (a member of MP Layla Moran’s staff), met with Council officers and their consultants WYG on 27 April 2018 to try to obtain answers to a series of questions about the proposed Seacourt P&R extension. Subsequent to the meeting there was a further email exchange and answers were provided to a number of outstanding points by the Council. We appreciate having had this opportunity for dialogue about the issues, and now feel we understand what is being proposed.
It’s clear from the response from the Council that the planning documents did not provide a clear reference to the use of an impermeable membrane at the site. It wasn’t spelled out in the application, and the documents give no details of the tanking and how this would work. This has now been explained to us.
We believe we should have been able to get answers, as of right, on points of issue like this through the planning consultation. The fact that we couldn’t was a failure of the process, and below the standards we have observed in other applications locally. The County (LLFA), Environment Agency and planning officer didn’t, in our view, fully understand what WYG were proposing – this is clear from correspondence with them during and subsequent to the planning process. Councillors, therefore, approved a proposal which had information gaps in it on flood risk, and which they couldn’t have fully understood. In our view this happened because the planning outcome had already been pre-determined, and our queries were ignored because the process was designed to secure a particular outcome.
Now that we know what’s actually proposed, we don’t believe (as far as we can judge) that the development poses an immediate and direct flood risk to local properties, which is obviously a welcome outcome. But all development in Flood Zone 3B by its very nature creates a risk to the consistent and predictable functioning of floodplains. Hence planning policy, which incorporates learning outcomes from decades of previous developments in areas subject to flooding, prohibits such developments because the medium and long-term consequences can be unexpected and far-reaching.
We believe the development is inconsistent with planning guidelines – building in the floodplain and Green Belt – but recognise the planning officer advised otherwise, and that Councillors agreed with his interpretation. We regret that the Secretary of State did not choose to examine this issue, and believe the Council’s decision sets an unfortunate planning precedent. We also remain unconvinced of the need case.
The car park extension will be an additional source of pollution during a flood, and there is no way to stop this. This is undesirable, and a negative environmental impact. The Seacourt P&R extension is just to the north of OFAS which has an ‘environmental vision’ aiming to improve freshwater habitat – a vision the Council signed up to.
If the development goes ahead, we’ll be watching with interest to see how often if floods and how the local authority deals with this. At times of flooding the car park will be a potential source of risk to users and members of the public. We will also continue to be vigilant about further planning applications brought forward by the Council, as the process has left us feeling we can’t rely on the local planning authority, or members of Council planning committees, to safeguard the public interest. We hope public concerns will be better addressed should any similar situation arise in future.