Answers to concerns

Some people have had concerns about the Oxford Flood Alleviation Scheme – the Environment Agency have recently made this response which we thought people might find of interest. (To avoid making it even longer we have not included the questions but the answers should make it clear enough what the questions are.)

Design of the scheme 

The scheme has been designed to be as natural as possible and respects and works with the existing natural floodplain. It is not a concrete channel. It is not an ‘on/off’ channel but a passive design which allows the natural floodplain to carry more water when needed. Most of the excavated area will be planted with vegetation and provide valuable new habitat for the area. It is designed to increase the capacity of the floodplain to carry more water.

The Oxford Flood Alleviation Scheme will not increase flood risk to properties downstream of Oxford. The scheme does not hold back water (like a flood storage scheme) nor does it speed up water (like a deep narrow channel could do). We conduct detailed modelling, which is always independently verified, and this shows the scheme will not increase flood risk to properties downstream of Oxford. In addition, the Vale of White Horse District Council also commissioned a completely independent review of downstream impact. This was published in December 2017 and confirmed that the scheme will not increase flood risk to downstream properties.

Willow Walk 

We will be removing the existing culverts and their metal railings, shown below and will install a new bridge in their place.

The existing Willow Walk track is already raised above Hinksey Meadow. The new bridge will continue from this track, just raised slightly higher, and will span 19 metres. The height of the deck of the bridge will be approximately 1.5 metres above the existing footpath. The bridge needs to be this size to allow flood water to pass underneath it.

We recognise the importance of Willow Walk as an historic route and a key east-west link for pedestrians and cyclists into Oxford City. Access will be needed for occasional maintenance vehicles. We have confirmed previously that there are no plans to turn Willow Walk into a road.

 Green Belt

If the scheme is approved we believe it will help to safeguard the Green Belt in this area as it will need to remain as a functioning flood alleviation scheme for at least the next 100 years. This will help to maintain and preserve the openness of this part of the Green Belt. The natural design for the scheme includes the creation of over 20 hectares of new habitat. The scheme aims to bring a long term green legacy to the area.

 Maintenance

The scheme will have a long term maintenance plan for the lifetime of the scheme, 100 years. This includes managing the vegetation in the area by grazing. The ‘second stage’ wider part of the channel has been designed to be grazed by cattle to create floodplain grazing marsh. Temporary fencing and removable barriers will allow the second stage channel area to be grazed. We will also create many wetland features within the second stage channel to maximise available habitat for wetland and aquatic species. The backwaters, scrapes and ponds will have a variety of depths, dimensions and gradients, to encourage diversity of wetland wildlife.

Existing streams

The new flood alleviation scheme does not divert water away from Seacourt, Bulstake and Hinksey Streams. The scheme lowers the existing natural floodplain so that in the event of high flows it can carry more water. In the Hinksey Meadow area, the existing Seacourt Stream will act as the first stage channel.

Managing excavated material

A Materials Management Plan has been submitted as part of the planning application. This plan explains the options we considered for both the management of the materials excavated as well as the options for transporting the material from the site. There are no plans to use North Hinksey Village to divert traffic or transport materials. We will construct a haul road specifically for construction traffic within the scheme area to reduce the need for lorries to drive on local roads to access different areas of the site. However, we will be removing a large amount of material which will need to remove from site. Lorries will leave the site via a new compound and access road at South Hinksey and join the A34. This will be our main compound and access point onto the road network.

The majority of the material being excavated will be alluvium, a silty clay. We will reuse this material in the proposed flood embankments where possible. Excavated gravel will be re-used in the scheme for environmental improvements and on the channel of the new river bed.

Most of the material leaving the site will be transported to old quarries and will be used to restore these sites. Once planning permission for the scheme has been granted we will be able to confirm which sites have the capacity and necessary permissions to receive the material.

Tree planting

To mitigate for the estimated 2,000 trees that will need to be felled during construction, we will be planting 4,325 trees. Approximately 15,000 smaller tree species, such as hawthorn, hazel and elder, will also be planted, along with many more native shrubs such as dogwood, goat willow, dog rose and wild privet. The tree-planting proposals result in more woodland within the scheme area after completion, than there currently is at present. 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.

The replacement woodland trees will be saplings and it will be many years before they have the same ecological value as those being felled, so throughout the design process, our contractors, engineers and ecologists have worked together to minimise tree loss wherever possible. Once a contractor has been appointed we will work with them to further minimise losses of mature trees wherever possible. The contractor will also protect all retained trees and hedgerows within the scheme boundary by erecting stout fencing before materials or machinery are brought on site and before any work starts.

The Environment Agency is committed to the scheme bringing additional environmental benefits beyond reduced flood risk, and this includes our consideration for the trees and wildlife across the scheme area.

Dredging

Dredging the River Thames would not significantly reduce flood risk to Oxford. Even if we dredge all the channels that currently exist in Oxford, it would not reduce flooding from a major flood. In many cases, dredging isn’t the best long-term solution because rivers can quickly silt-up again. It can even increase flood risk downstream, alter the ecosystem, be environmentally damaging, costly and disruptive. Studies have indicated the River Thames would require frequent re-dredging as the natural tendency of all rivers after dredging is to deposit silt and return to their more natural dimensions. And it would not be a cheap option to dredge the River Thames.

 

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.

 

Seacourt – Possible Costs

This seems a potentially costly proposal.

Capital 

1) Present budget £4.1 million

2) Difficulty of building in low-lying ground with a high groundwater level in winter

3) Possible need to stabilise unstable ground by treating it with lime to a metre depth

4) Difficulties of creating a working SuDS in a flood plain

Income

5) Occupancy likely to be low

6) Periodically out of use due to groundwater and fluvial flooding, pumping out, repair and maintenance

Maintenance

7) Pumping out (will be required according to the Applicant)

8) Repair of damage to surfaces and buildings – may be extensive after major floods

9) Cleaning and restoration of the porous surfaces required for SuDS

Other

Given the risks associated with large floods and the likely depths and flow rates here, possibly

  • compensation for damage to vehicles, including any swept away
  • compensation for loss of life.

Thoughts on OFAS

Why do we need a flood scheme at all?

We have had five major floods since 2000 and climate change will make things worse (indeed there is evidence from Oxford University that it already has). Oxford residents, and the economic well-being of the City, will suffer badly if something is not done. While the scheme will cause disruption during its construction it is imperative that Oxford is protected.

But what about downstream, won’t they be worse off?

All the detailed computer modelling for the Scheme (and we have recently heard on the grapevine that a totally independent consultancy has confirmed this ) says that flooding will not be made worse downstream. We know that comparisons are made with the Jubilee River – this scheme is nothing like that. Indeed OFAS is actually increasing the capacity of the floodplain, which together with bunding and rerouting of flow will reduce flood risk to many hundreds of properties.

Is it a concrete channel?

No, it isn’t. What it is is a much more naturalistic 2-stage channel, used around the world for flood relief.

How will the environment be affected?

While there will, regrettably, be some environmental losses, we are pressing hard – collaborating with the Environment Agency, and with support from others, particularly the Freshwater Habitats Trust – for environmental enhancements as part of the scheme. While one cannot compare one environmental loss directly with another environmental gain we believe the positives will be considerable.

Maintenance.

It’s so important that there is a plan now for the very long-term maintenance of the Scheme. In our experience over the last 10 years  “if maintenance can be neglected it probably will be”. There are some honourable exceptions and we certainly have we have no criticism whatever of the local EA maintenance team, who achieve a huge amount with very limited resources. Others do nothing or very little unless goaded and embarrassed into action. This Scheme, being “natural” will deteriorate quickly if not proactively maintained. The initial intent was to plan maintenance for 10 years: that is simply not good enough for such an expensive and important project. We have proposed that maintenance be planned for in perpetuity by setting up a responsible, funded, local body, maybe as a charitable trust (or similar).

A Green group

thinks that Oxford could and should be protected by very different means – while they are short on specifics, their main idea seems to be that planting enough trees upstream in the Cotswolds would solve Oxford’s problems. It wouldn’t. Expert opinion at our 2015 Symposium of Natural Flood Management (NFM)  made that very clear. Even afforesting the whole of the Cotswolds (not that that would ever happen) would not do the job. Oxford is simply too far downstream for that. That’s not to say that NFM can’t work in smaller catchments, nor that it might not make a contribution.

Flooding land upstream?

The Environment Agency’s Oxford Flood Risk Management Strategy (OFRMS) suggests this may be needed one day if climate change makes things sufficiently bad. Involving as it would temporary flooding large areas of farmland and other land it is never likely to be easy to implement.

 

 

Maintenance and wildlife

We met with the Environment Agency (EA) and Jeremy Biggs of the Freshwater Habitats Trust (FHT) today.

We talked about articulating an environmental vision for the Oxford Flood Alleviation Scheme (the Scheme) which brings together the various initiatives which are planned and how these will be managed and maintained. This included possible bodies/corporate structures that might be involved in overseeing maintenance in the long-term, to deliver both flood risk reduction and benefits for wildlife. We are working towards a preferred option for the future management arrangements.

FHT is hoping to facilitate community involvement in the conservation of freshwater habitats within the Scheme area – for example by employing someone to liaise with local people, including schools, so they can be involved in wildlife science in the floodplain. Part of the funding has been secured by a generous offer of funding from Thames Water, and FHT and EA will now approach other bodies together.

OFA is about to send letters asking local businesses to contribute funding to help close the small funding gap that remains for the Scheme.

Our comments on Oxford Local Plan 2036

Oxford Local Plan 2036
“Oxford City Council is producing a new Local Plan for Oxford. The Local Plan is important because it will shape how Oxford develops.” (from the ‘Preferred Options’ document for the Plan, Oxford City Council). The Council called for comments and we wrote recently as follows:

We wish to submit the following comments in relation to the proposed Oxford Local Plan 2036. Our comments all relate to flood risk.

Overall we are satisfied that the City Council has adopted an appropriate strategic approach to development and flood risk in the city, with new development targeted towards areas least at risk from flooding. We welcome the recognition in the document that flooding is a significant risk for the city and that this needs to be managed.
 
On the specific sections relating to flooding in the Preferred Option, we would like to see reference to the need to actively maintain watercourses in the city so that they function freely during times of flooding. We’re surprised that the SFRA Decembrer 2016 makes no mention of the need for clearing of trash gates, and the removal of vegetation and fallen trees from streams and ditches. Riparian owners in the city need to be encouraged to maintain water courses.
 
On Option 38A we would prefer to see adoption of a policy which states that there will be no development of previously undeveloped land in flood zone 3b. As the SFRA notes, this is the position in the current Core Strategy and we see no argument for weakening this.The new plan does not designate greenfield sites in zone 3b for development.
We recognise that water compatible structures and essential infrastructure may, in exceptional circumstance, be permitted in zone 3b under the NPPF. But the Council’s recent attempts to argue that an extension to the Seacourt Park & Ride constituted ‘essential infrastructure’ caused the Oxford Flood Alliance considerable concern. While references to NPPF in the Council’s proposed Local Plan may appear to provide safeguards to the public, these are significantly weakened if the Council intends to ‘interpret’ NPPF along the lines argued for the P&R extension or similar. We believe the plan document needs to provide clarity on this.

 If Preferred Option 38A is adopted as proposed we wish to state for the record that we interpret this to mean that NPPF will be strictly applied. It is clear in Table 2 and 3 in this Guidance Note what ‘Water Compatible’ and ‘Essential Infrastructure’ mean. We are therefore interpreting the Council’s policy to mean what the NPPF guidance says it means. This does not include car parks.

In Option 56A we would like to see a reference to riparian owners responsibility to maintain water courses. Simply treating them as a design feature isn’t sufficient.

 

OFA Steering Group

OFAS: Environmental meeting

Attended an environmental update meeting yesterday, organised by the EA with a number of local environmental stakeholders attending. A lot of thought is going into making the most of possible environmental enhancements that the Scheme can bring.

Led by Penny Burt of the Environment Agency we covered surveys, ecological trial areas, archaeology, low-flows and existing watercourses, fish passage, Hinksey Meadow, trees and bridges, habitat creation and access. Also mentioned was future maintenance – we felt that the plans were not nearly long-term enough and this was discussed.

For our part we are working closely with the Freshwater Habitats Trust. The Oxford area is rich in freshwater species, though there is, nevertheless, a long term decline: this Scheme could help reverse that trend. We’d like to give the public, including school children, a chance to be involved, including with data collection in the field – sometimes called ‘citizen science’.

The damselflies in the photographs are closely associated with the freshwater habitat.

Maintenance of Weirs Mill Stream

Environment Agency contractors have been working on the Weirs Mill Stream and nearby this month. We helped identify the need for this maintenance (see 2015 APM report para 3). The work will  improve conveyance of water through this important part of the Oxford river network. It is above and beyond the usual annual maintenance programme and is being paid for using additional funds which the Environment Agency received from The Treasury following last winter’s flooding.

 

Further comment on Network Rail’s planning application for track-raising

We submitted our comments on the latest revision (A02) of Network Rail’s flood risk assessment (FRA) for their planning application for track-raising yesterday.

The planning application is number 15/03703 and details can be found on Oxford City Council’s planning portal https://www.oxford.gov.uk/info/20066/planning_applications/328/view_and_comment_on_planning_applications

The application is going to West Area Planning Committee for determination on 3 May at 2 pm at the Town Hall.

See also our earlier post https://oxfordfloodalliance.org.uk/2016/03/28/network-rails-planning-application-for-track-raising/