Oxford City Council has issued a draft Supplementary Planning Document for the development of the western end of the city centre, an area which includes Osney Mead. The council is inviting comment. The relevant documents can be found here: https://www.oxford.gov.uk/news/article/2217/council_invites_views_on_latest_stage_of_major_transformation_of_oxford_west_end_and_osney_mead.
Osney Mead floods and will continue to do so even after the Oxford Flood Alleviation Scheme is built. How flood risk will be managed as plans come forward will need very close scrutiny. OFA believes the SPD should be strengthened in a number of areas to set an appropriate framework for managing potential future flood risk, including from sewers. We also believe the approach to biodiversity needs strengthening in line with the approaches adopted by the Oxford Flood Alleviation Scheme. OFA has submitted the following comments to the City Council:
a) Flooding and flood risk – the documents acknowledge that Osney Mead floods and will continue to do so after the completion of the Oxford Flood Alleviation Scheme, and that any development there needs to create capacity to contain and manage flood water. This can only be done, the documents say, if the whole Osney Mead site is developed in a joined-up way. The documents also recommend the creation of the appropriate infrastructure before any other development. We strongly support this view. Management of flood risk needs to be taken very seriously in any plans which come forward, not just for Osney Mead itself but also for adjoining areas. There is a risk that piecemeal re-development of the site could increase flooding locally and it would be challenging to monitor and manage.
While we welcome the general statements made about flood risk we do not see how some of the descriptions and images of proposed redevelopment on Osney Mead are consistent with flooding of the area. We therefore have serious questions about how well flood risk has been understood by the authors of these documents. In particular, the documents talk about ‘activating’ the riverbank south of Osney Lock and down to Grandpont. The proposals envisage a new, wider cycle and pedestrian route along here, river-facing buildings (apartments, offices) and new spaces for people to sit. The illustrations of what this might look like show a heavily urbanised and landscaped river frontage with paths and building all at the same level. But the towpath floods most years and is often impassable. This is flood zone 3b, part of the natural flood plain, and the types of development permitted in such an area by the National Planning Policy Framework are very restricted.
How can the envisaged ‘activated’ frontage as illustrated in these documents possibly be realised in these circumstances? Will the bank be raised to create the kind of structures shown in the SPD? If so what happens to flood water which currently overtops the Thames banks and inundates adjacent areas? Canalising the Thames at this point would create significant flood risk for existing communities both up and downstream of the area. Or will the riverside path remain at existing levels and be allowed to flood? This is very unclear in the documents. We would like to see explicit statements in the SPD and design guidelines about the challenge of ‘activating’ the riverbank given that it is in flood zone 3b. Illustrations in the documents should also present a more realistic view of what the redevelopment might look like.
The design guidelines talk about new bridges connecting the towpath by the Punter to Barret St on the other side of the Thames, and one at the eastern end of South St crossing the Osney Stream to connect to Osney Mead. In both of these locations temporary flood barriers are currently deployed when river levels are high. These barriers are critical to preventing houses on Osney Island from flooding. At the end of South St there is a large wall where the proposed new bridge would come across. This wall helps to contain flood water in Osney Stream. The demountable flood defences for the island are stored in the EA’s Osney depot. If this depot is to close and move we need to understand how flood defences will be deployed during a flood emergency. A large pump located on EA land behind the houses on the eastern end of South St is also a critical part of the local flood defence system. This pump evacuates flood water from the island and pumps it into the weir pool. Even after the completion of OFAS houses on Osney will continue to be vulnerable to flooding and temporary defences will still be required. We would like to see the SPD/design guidelines explicitly state that any developments must not compromise flood defences for Osney Island.
A holistic approach to redeveloping Osney Mead potentially creates an opportunity to help reduce flood risk to Osney Island as well as addressing the challenges of the Osney Mead site itself. We would like to see the SPD flag up this opportunity as something to be explored. We have a rare opportunity to reduce risk for vulnerable Osney residents and this should not be missed.
Redevelopment of the Castle Mill area could potentially affect streams and weirs in that section of the city. Any plans coming forward should ensure there is no reduction in the capacity of these streams to help move flood water through the city. Could the performance of these water courses be improved to help alleviate flood risk in the city? Has this been considered?
b) Sewers – the current sewer system on Osney Mead does not cope with floods and is quickly infiltrated by flood water. Sewage is pumped from Osney Mead up Bridge St on Osney Island to join the main sewer on Botley Rd. In a flood the pressure in the system means sewage bubbles out of the sewer covers and has to be pumped into the river. Some people on Osney Island cannot use their toilets during a flood. We raised this issue in a previous consultation but there is no mention of sewer infrastructure in the Supplementary Planning Document or the Design Guidelines issued for consultation.
We need assurances that adequate sewer infrastructure will be put in place and this must be a prerequisite for any redevelopment of Osney Mead. The increased density of proposed redevelopment will greatly increase pressure on the sewer system. Failure to address this infrastructure requirement could be disastrous for some Osney residents and would mean regular discharges of sewage into the local wate ways to the detriment of the wildlife. When we have tried to raise these issues with Thames Water in the past they simply say ‘it’s caused by fluvial flooding which is nothing to do with us’. We know what an appalling track record the water companies have on river pollution. A holistic approach to the redevelopment of Osney Mead must include addressing the sewerage problems, including using flood mitigation measures to reduce risk of sewers being infiltrated.
c) Biodiversity – throughout the development of the Oxford Flood Alleviation Scheme we have been strong supporters of the ‘environmental vision’ of the scheme and the idea of making the new stream as natural as possible. This helps reduce long-term maintenance of the assets being created and is far more sustainable than a more engineered approach. We believe a similar approach should be adopted for Osney Mead. The design document talks about ‘sensitivity to habitat’ and of retaining ‘existing trees where possible, especially those of good ecological and amenity value.’ A glance at Google Earth shows the two main areas of tree cover on Osney Mead are along the bank of Osney Stream opposite the houses in Bridge Street extension, and along the towpath south of Osney Lock down to the railway bridge. The SPD seems to envisage the elimination of all of these trees. This is a major contradiction in the documents. Removing them would take out most of the existing habitat. There is a considerable difference between the carefully thought through strategies in OFAS for how biodiversity will be enhanced through the project, and the vague reliance on street trees and green roofs in the SPD design document. Green roofs need regular maintenance including irrigation and addition of fertiliser. There are some positive words in the design guideline but protecting and enhancing existing biodiversity in the area, including incorporating wild, unmanaged space into the design, hasn’t been adequately thought through. Continuing to allow the river frontage to operate as natural floodplain as it does currently, with the trees and other wild vegetation retained, would be less environmentally destructive and cheaper to maintain. We would like to see approaches here better aligned with OFAS’s approach to enhancing biodiversity. The SPD should include explicit references to OFAS and its environmental vision, and alignment with this should be a requirement of any developments coming forward. The OFAS project covers an area which borders Osney Mead and includes important targets for new wild flower meadows in the area. Opening access into the greenbelt from Osney Mead must not compromise the biodiversity targets OFAS is committed to delivering.