Flood compensation for new Oxpens development

The proposed redevelopment of the Oxpens area involves the lowering of some land to compensate for the raising of other areas to lift them out of the flood plain. The initial round of consultation in the summer attracted a fair amount of comment on the need to preserve floodplain capacity as this helps reduce risk of property flooding.

A new set of consultation documents has just been issued and OFA is pleased to note that flood compensation has been calculated on what is known as a ‘level for level’ basis. In other words any land which is raised will be compensated for by lowering land within the same height band elsewhere on the site. We understand the Environment Agency insisted on this.

One of our major concerns with the Seacourt Park & Ride extension was that compensation was not calculated on this basis resulting in a loss of floodplain capacity. The Environment Agency allowed this at the time despite our protests. We’re please that for this new development the appropriate industry recommended approach has been adopted. The compensation includes an additional allowance for climate change and should help with reducing flood risk in the city if the development goes ahead.

Sewer flooding in Campbell Road

Residents in Campbell Rd, Florence Park, had their gardens flooded by sewage on 21 October in a near repeat of a similar event last year. This time round Larkrise Primary School had to be shut for a day. https://www.oxfordmail.co.uk/news/19662645.larkrise-primary-school-oxford-closed-due-sewage-leak/

Overflowing sewers are a long standing problem in the area.  Earlier this year OFA supported local residents in organising a meeting of relevant agencies, chaired by MP Annaliese Dodds, to discuss solutions. This followed a serious incident on 3 and 4 October 2020 when gardens were flooded with sewage to a depth of 60cm. Some sheds and home offices were affected, causing misery for people working from home because of Covid.

The meeting, which involved Thames Water, the City Council and the Environment Agency, was constructive, but progress since has been slow. A report which Thames Water should have completed on the causes of the 2020 floods has still, it appears, not been provided to the Council. The clean-up response to the events a few weeks ago again showed the company apparently unable to deal with the community other than on a customer by customer basis.

OFA is supporting the community in trying to get a number of short term measures adopted to ease the situation while a wider solution is worked out. The sewage released in these events spills into Boundary Brook which enters the Thames downstream of Donnington Bridge, adding to the levels of pollution in the river.

Flood risk increasing says Environment Agency

‘Significant climate impacts are inevitable especially for flood and coastal risks, water management, freshwater wildlife and industrial regulation,’ says the latest Environment Agency adaptation report published earlier this month.

According to the latest projections, summer rainfall in the UK is expected to increase 22% by 2080, and winter rainfall by 13%. The report sets out what the agency is doing to help reduce flooding of properties and businesses, ensure future drinking water supply, reduce pollution, and protect the biodiversity of freshwater habitats. The  Oxford Flood Alleviation Scheme (OFAS) features as a case study in the report, an illustration of the kind of action the EA is taking in partnership with others.

Early action is needed the agency warns: ‘Despite more than a decade of concerted effort to reduce these risks, the speed and scale of climate change means that many are either increasing or remain significant. This broad conclusion matches recent assessments from the Climate Change Committee, the Intergovernmental Panel on Climate Change and others.’

The OFAS scheme will be submitted for planning approval this winter. The planning documents will incorporate the latest government assumptions about future rainfall and flood risk.

High river levels test flood preparedness

In the first week of February we’ve experienced the worst flooding in Oxford since 2014. The coordinated response from the Environment Agency and local authorities shows how far we’ve come in recent years in the management of flood events. We owe them a big thank you.

Back in the early 2000s flood management was reactive and often disorganised. But lessons were learned and we now benefit from much better levels of preparedness, and good cooperation between the various agencies. We also benefit from the infrastructure put in place to divert water away from houses, and from regular clearing of water courses of fallen trees and flood debris.

Bulstake Close barrier and pump

The high level of flooding this year has provided a robust test of flood management procedures. With UK winters getting wetter and wetter we can expect more of these type of events and bigger ones, so it’s important we continue to refine the response to make it as good as we can get it. This is something OFA is actively working on. The flood alleviation scheme is still some years away.

A major weak spot currently is the slow response of Thames Water to residents experiencing sewage leaks. We have had reports of sewers in various locations overflowing as a result of the high flood water. Householders reporting these problems have found Thames Water difficult to engage. OFA is raising these issues with the various bodies responsible for flood management. Oxfordshire MP Robert Courts has insisted Thames Water ‘must do more’ according to a BBC report. We agree.

Flooding from sewer South Hinksey

We also think communication to local residents during a flood event about what’s happening and what’s being done in response could be improved. These events are also an opportunity to educate residents, particularly new residents, about the nature of the flood risk in their area. OFA has initiated discussions about this with the Environment Agency and other interested parties.

At a local level the response in some specific communities can be further refined to ensure the most vulnerable households are known about, and receive timely and targeted help. The new barrier in South Hinksey had its first serious test. It did the job required of it but will need some further adjustments if it’s to be effective in a larger flood. The Environment Agency is looking at this.

We continue to be concerned about safety issues at the Seacourt Park and Ride extension once it is open. We believe there is a significant risk of cars being stranded in flood water there. The Seacourt Stream overflowed into part of the existing car park during the recent foods, leaving parked cars standing in shallow water. The bike rack by the bus stop was also flooded.

Cars standing in flood water at Seacourt P&R

Adrian Porter, from the OFA Steering Group, was interviewed on BBC Oxford on 5 February about the flooding across Oxford and about our ongoing campaigns.

Seacourt car park safety concerns

One important area of concern for us during the planning process for the Seacourt park & ride extension was the safety of users of the car park. The speed with which the site flooded on Christmas Eve underlines the risk here. In the planning application the Council argued that: ‘Historically, river levels have risen fairly slowly in this location even during extreme events, giving sufficient warning for mitigation measures to be put in place.’ But the recent flood did not conform to this pattern.

Are the Council’s safety measures at the car park robust enough? We doubt it. Had the park and ride extension been operating there would probably have been several cars bobbing about down there. Flood barriers were only erected by the City Council at Bulstake Close after the flooding had already happened.

At the peak of the flooding river levels were so high water from the Seacourt stream west of the existing car park started to encroach onto the parking area (see photo below). There were several cars parked there. Had river levels been higher these cars would have been stranded. Flood management plans for the park and ride need to be reviewed.

Seacourt car park extension flooding

The recent flooding of the extension to Seacourt Park & Ride is further evidence that the City Council seriously underestimated the vulnerability of the site to flooding. The area flooded rapidly during the night of Christmas Eve, and as of today is still partly inundated though water is now being pumped out.

View of the extension down the main access ramp on Christmas Day

The Flood Risk Assessment (FRA) submitted with the Planning Application stated: ‘An analysis of historic flooding incidents relevant to the site suggests that the site will currently flood roughly once in every 1.7 years and will remain out of operation for around 10 days during an average flood event.’ That’s just under 6 days a year average.

Over the course of last winter (2019/20) the site was inundated four times and for prolonged periods. This latest incident represents a further 12 days of flooding. In our opposition to the planning application we argued that the Council had grossly underestimated the likely extent of flooding at the site. Events seem to be proving us right.

Sewer flooding in South Hinksey

It is not uncommon for residents of Kennington, North Hinksey and South Hinksey to suffer from sewer flooding problems and these continued over the Christmas period with surcharges occurring on both the 24th and 27th December. Both dates coincided with the heavy rainfall events and result from Littlemore Pumping Station being unable to cope with the high volume of water.

The second surcharge was particularly challenging for South Hinksey residents as the EA flood barrier prevented the sewage from leaving the village. Thankfully the pumps the EA had already provided prevented houses from being flooded, but they couldn’t stop a pollution incident as the sewage discharged into the local water courses.

Several residents reported the incident to Thames Water, but their response time was well short of their two-hour target. We know of one call which was responded to eleven hours after being reported, and another which took a whole three days. We’d be interested in other readers’ experiences.

OFA Steering Group member Adrian Porter has once again raised the poor level of service with the Thames Water customer liaison team.

Christmas 2020 flooding

Residents in Wolvercote, West Oxford, North and South Hinksey and Grandpont witnessed significant localised flooding on Christmas day after a rapid rise in river levels over the preceding days. Between the 17 and 22 December, more than 25mm of rain fell across the upper parts of the Thames catchment resulting in high river levels on the Thames and the three main tributaries feeding the Thames – the Evenlode, Windrush and Cherwell. An additional 20-60mm of rainfall fell between the 22 December and the 24 December on the already saturated Upper Thames catchment causing a rapid rise in river levels on the Thames in Oxford. The large volume of water discharging from the Cherwell to the west of Christchurch Meadows, is thought to have caused flood water further upstream in Oxford to back up, contributing to a faster rise in levels than we typically experience in the city.

After peaking on Christmas day levels fell, but further rainfall on Saturday night nudged levels back up. The rivers seem to have stabilised since and levels are expected to fall in the coming days. The peak level of the recent flooding was significantly higher than those seen during last winter’s flood events. The Environment Agency has been actively monitoring the situation and flood barriers were erected in South Hinksey as a precaution. Flood Warnings were issued for Wolvercote, and for the New Botley – North/South Hinksey – Grandpont areas. There have been no reports of properties in the city flooding.

The speed at which river levels rose on Christmas eve is particularly concerning, as this limited the amount of time available to deploy defenses. This has potential implications for future flood management planning.