Risk of local property flooding

From the Planning Officer’s report to the West Area Planning Committee, December 2017:

“9.149. During the consultation process, reference has been made to the suggestion within the Factual and Interpretive Ground Investigation Report that the proposed drainage strategy will require the use of lime stabilisation to avoid damage to the paving within the car park expansion from changes to the clay layer below ground and that this needs to be given further consideration as part of any drainage proposals for the site. The concerns raised are that lime treatment is likely to have an impact on the permeability of soils below the car park, and therefore needs to be appropriately considered. 

The applicant has confirmed that the surface water drainage strategy has been designed as a tanked system which assumes no infiltration below the attenuation layer, with all storm water discharge from the site via a controlled outfall into Seacourt Stream. An impermeable membrane is included within the construction to prevent water saturating the clay. The underlying clay is of a low permeability whether lime stabilisation is employed or not, and it is envisaged that the attenuation will operate effectively in either scenario.” [emphasis added]

There is no mention in the Application of tanking, nor of an impermeable membrane. We have therefore not known of this till very recently and had no opportunity to comment. While there is little or no detail, the idea that the car park may be separated from the underlying groundwater table, as this implies, raises an extremely serious question. That is, where will the displaced groundwater go? This is a lot of water over such a large area. It is likely that it will cause a significant rise in groundwater levels around this low-lying site. This could cause (new) groundwater flooding within houses (and gardens) nearby. No decision should be taken until the details of  what is planned are made clear, appropriate calculations and modelling done, and presented as part of a further revised Flood Risk Assessment.

[By the same token, when it rains, water will be trapped within the tanking , draining only slowly – more pumping needed?]

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Objecting to Seacourt P&R extension – our latest comments

 

We remain strongly opposed to the planning application by Oxford City Council to extend its Seacourt Park and Ride into Oxford’s vital flood plain. There has been a nibble, nibble attrition of the flood plain over many years leading to worse flooding. That the City Council should itself be seeking to extend a car park into the flood plain that protects our city is quite extraordinary.

Here are our latest comments:

OFA comments on FRA Nov 2017 Final

OFA comment on PS Addendum Nov 2017 Final

Redbridge vs. Seacourt P&R from south + Maps

Letter to EA 30 November 2017_final

Lime stabilization considerations Nov17

Meeting with Anneliese Dodds, MP for Oxford East

We met Anneliese Dodds, new MP for Oxford East earlier this week. We had a very useful discussion on a variety of flooding topics, including the Oxford Flood Alleviation Scheme, that we are going to be approaching local firms for financial support for the Scheme, our interest in environmental enhancement as part of the Scheme and in establishing a local body responsible for its maintenance in perpetuity.

We explained our serious reservations about the proposed extension of Seacourt P&R into the functional flood plain (Flood Zone 3b) and what we see as a flawed Flood Risk Assessment. Such an extension could not only affect flood risk itself but set a precedent which might lead to further encroachment onto the floodplain with potential further increase in flood risk. Anneliese will look at the revised planning application which is expected in due course.

We look forward to working with Anneliese in the future.

Letter to the Oxford Times (8 Dec)

Letter from us published in the Oxford Times of 8 December 2016

The proposed extension to Seacourt Park & Ride is one of the worst planning proposals we’ve seen for some time. In 2013, after much public consultation, the City Council adopted a Core Strategy to guide development in the city over the next period. Core Strategy 2 includes the statement: “Greenfield land will not be allocated for development if any part of the development would be on Flood Zone 3b.” The proposed extension to the Park & Ride is a greenfield site in Flood Zone 3b, the functional flood plain. How can this be? The planning documents don’t explain. Although the documents include a review of relevant local policies, Core Strategy 2 mysteriously doesn’t get a mention. What’s driving the application is a worry about short-term problems with traffic congestion on the Botley Rd pending completion of new Park & Rides at Eynsham and Cumnor. How does this short-term need justify departing from core strategy? National planning policy is designed to encourage local authorities to take a strategic approach to planning, thereby avoiding the need for this kind of last minute quick-fix nibbling away at the floodplain.

Apart from the obvious conflict with planning policy, the application is riddled with errors. The Flood Risk Assessment says that the most recent flooding event at the site was 2008, ignoring the major disruption in the winter of 2012/13, and the serious floods in early 2014. The FRA completely fails to take account of the fact that the site floods frequently, and proposes a design which will quickly degrade as a results of flood damage and silting. There is serious risk in the event of a major flood of large sections of the car park breaking up and washing into the flood channel. It’s a nonsense and needs to be stopped.

Application by Oxford City Council to extend Seacourt Park & Ride

Application by Oxford City Council to extend Seacourt Park & Ride  (Oxford City Planning application no. 16/02745/CT3).

We are strongly opposed to this application to build a car park extension right in the Oxford floodplain.

Our key points are:

Inappropriate development in the floodplain – contrary to Oxford City Council Core Strategy, CS2 – this is a greenfield site. It is also contrary to City Council Core Strategy 11 – it is neither ‘essential infrastructure’ nor ‘a water compatible structure’.

Not consistent with national planning policy framework (NPPF) guidelines.

Inappropriate development in the Green Belt.

A planning application for a similar scheme on the same site was rejected by the Secretary of State in 1999. Planning law has become tighter since.

County Transport Strategy envisages new P&R sites at Cumnor and Eynsham over the next few years; the present proposal is at variance with that. Traffic coming off the A34 and A420 may face increased delays in reaching the P&R.

Flood-risk assessment flawed:

  • fails to note the serious floods since 2008
  • does not properly consider the frequency with which this low lying site actually floods, which is often (it’s functional floodplain)
  • permeable pavement recommended only slows run-off when flood event are so low risk it’s irrelevant. As soon as a significant flood event starts to develop the car park will be under water.

Emergency evacuation plan is inadequate and lacks detail. The site is at high risk of flooding, being 0.5-1 m lower than the existing car park. There is a significant risk to vehicles and people during a flood event: any emergency plan has to be very robust. Extra resources could be needed from already stretched emergency services. In a 1 in 100 flood the water would be 2m deep.

The ground is subject to movement and would require further investigation to see if remediable stabilisation would even work.

The site itself may be damaged by prolonged or severe flooding, even with surfaces broken and swept away. The fences proposed for the perimeter of the 2 ha site, and structures on the site, would be very vulnerable in a large scale flood.

The proposed permeable surface will be impaired by silt and other debris: it will require cleaning which may or may not restore its permeability. After prolonged flooding such paving may even have to be replaced (in early 2014 this site would have been under a significant depth of water for several months).

If fences, structures on the site, and cars were swept away they could end up blocking the nearby Seacourt which is a vital flood channel.

The proposal does not take proper account of the latest plans for the Oxford Flood Alleviation Scheme in this area.

The rationale for this extension being needed is that the present car park cannot be given a decking storey because of a covenant on the land. No such covenant has been produced by the applicant and we cannot find one. What there is is a lease agreement, with could potentially be varied by negotiation with the landlord, which could make this whole scheme unnecessary.

Oxford is at risk of flooding. The principle of not building on greenfield sites in the floodplain must be adhered to.

These reasons are set out in more detail in the following documents submitted to the planning authority, Oxford City Council (links download pdfs).

  1. Our initial objections (28 Nov 2016)
  2. Further points (5 Dec 2016)
  3. Address to Council (5 Dec 2016)

We are working hard to get our message across to the decision makers and to other people who may wish to comment. If you agree with us that this development should not be allowed to go ahead please do say so via the Oxford City planning website or speak to your local City Councillor.

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/

Network Rail’s planning application for track-raising

Network Rail (NR) has applied for planning permission in relation to its plan to raise a particularly low area of the mainline track to London, beneath and either side of the old Abingdon Road bridge (Redbridge) near Kennington, to reduce the risk of the line flooding. Doing only this would increase the risk of flooding to the west of the line by raising the height of what is already a dam to the free flow of flood water. So NR propose a new culvert beneath the railway to compensate for this.

We have no objection to this plan in principle, but it must be done properly to ensure that the flood risk to properties and roads is not increased. If the mitigating culvert is too big areas to the east would be affected, too small and those to the west would suffer.

NR then need to convince the planning authority that their proposal gets the balance right and does not increase anyone’s flood risk. This is done mainly by modelling of flood flows and levels and reporting the results as part of a Flood Risk Assessment (FRA) which is at the heart of the planning application. This was first submitted in February. We went over this with a fine-tooth comb and found gaps and serious inconsistencies in the data presented. We did not believe that the document allowed the necessary judgement to be made, indeed it raised more questions than it answered. We made a submission to the planning authority, Oxford City Council, suggesting that, on the available evidence, it would be unwise to allow the application. The FRA, our comments, and many other documents can be seen on the council’s planning website – application number 15/03703/FUL. Our comments: OFA comments on 15/03703/FUL – Construction of a culvert.

A revised FRA (Revision AO1) was tabled by NR on 25 February in response to comments made by the Environment Agency to them. Because of the timing this revision  did not deal with our questions. We submitted further comments on AO1, reiterating and expanding on key points, on 9 March. We again gave our opinion that the evidence presented in the FRA was such that it could not allow a safe and proper decision to be made. This submission: 15:03703:FUL OFA Comments on the revised FRA (revision AO1, Feb 2016) F

After making our second submission to the planners we met with representatives of NR and their advisers. They confirmed that there were indeed the errors we had drawn attention to, in both the original and AO1 revision of the FRA. They said they had identified the reason for these errors and explained this. We understand that they will be filing a further revision, plus an amended version of an associated document, GRIP3, which is referred to in the FRA.

We have discussed our concerns with the planning officer at the Council who has been helpful and attentive to our arguments. A decision on the application has now been deferred to allow time for the revised documents from NR to be reviewed by the public and by Council planning staff.

Postscript: we were later asked to review the maps associated with the FRA, to compare what the model suggested with what we know ‘on the ground’. Our comments: 15:03703:FUL – OFA Review of flood model maps.