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.

OFA Update / OFAS & Flood Exercise

This update has recently been sent to those on our mailing list.

Dear OFA contact,

We last sent out an update in Oct 2019, just after the news about the problems with the A423 bridge (southern bypass) and likely delays to the Oxford Flood Alleviation Scheme (OFAS). OFA is still active and has been participating in meetings of the Sponsoring Group for the OFAS scheme and has also held separate meetings with the Environment Agency team about water course maintenance since our last update.

Despite the A423 issues, and the challenges presented by coronavirus, the OFAS scheme continues to progress. The EA and the County Council have agreed a collaborative approach to replacing the A423 bridge and constructing the OFAS scheme. This should save on costs for OFAS, and reduce the level of maintenance required in future.

The EA withdrew the original planning application earlier in the year and is currently revising this to incorporate the new A423 arrangements, and to update the documents on some other aspects of the scheme. Once these are resubmitted to the planning authority the public will have a fresh opportunity to comment on the plans. The EA is continuing to meet with objectors to the scheme with a view to trying to address outstanding areas of public concern.

Because OFAS is now expected to be delivered two years later than originally expected it is important that effective flood response procedures are in place in case a major flood event happens in the next few years. The EA, Fire Brigade and the local Council officials will be holding a practice response on 20 August to test aspects of current procedures. Because of coronavirus these will not involve the pubic.

The text of a recent update from the Environment Agency is pasted below which provides some additional information on OFAS and other matters,

OFA Steering Group

Oxford Scheme update

A423 bridge replacement

Oxfordshire County Council began the propping work on the A423 Kennington Railway Bridge in July.

Replacement of the A423 Bridge has provided an opportunity to design and build the bridge and the flood scheme together. This allows us to reduce disruption during construction and ensure the best use of public money. The updated design will use open channels instead of culverts to allow the flow of floodwater under the bridge. This will provide a better environment for wildlife and requires less maintenance.

The bridge is at the southern end of the scheme and during a flood, water would need to pass underneath it to re-join the River Thames. This capacity needs to be in place before the scheme is constructed to avoid increasing flood risk elsewhere. We also need to have all approvals, including planning permission and our Compulsory Purchase Order secured.

South Hinksey Archaeology

If you’ve been walking near South Hinksey, you may have spotted our contractors on site. We are carrying out archaeology surveys in a field near South Hinksey village to check whether the area is suitable for us to use as the main compound for when we construct the scheme. The archaeology surveys will determine whether there are any historical artefacts in the field. We want to ensure there’s no risk of us damaging any artefacts or remains. Once we have finished the investigations, we will remove our equipment from the site and reinstate the fields.

Kendall Copse Ground Investigations

To complement the new A423 bridge replacement, we are reviewing the design of the scheme around Kendall Copse, near Kennington.

From 10 August, we will be digging trial pits and drilling boreholes to understand the ground conditions beneath the site in order to finalise these designs.

Oxford Flood Incident Exercise

To ensure our flood protection plans are well-tested, the Oxford Flood Alleviation Scheme partners and emergency responders will be practicing their incident response plans on 20 August 2020.

The flood response exercise will consist of:

 •temporary flood barriers in South Hinksey and Bullstake Close

•pumps to remove flood water along Botley Road

Due to the current Government guidance on public gatherings, we won’t be able to invite members of the community to attend. We will be sharing updates on Twitter and Facebook as the exercise progresses. We will also share video footage of the temporary barriers and pumps so you can see our field teams in action.

Managing your flood risk

During the summer months, flood risk might be low on your list of priorities, but Environment Agency officers are thinking about it year-round. Throughout the year our operations staff carry out inspections and clear debris to keep main rivers moving. To report a blockage that could cause flooding call our 24 incident hotline: 0800 80 70 60.

You can also find out what maintenance is planned in your area: environment.data.gov.uk/asset-management/index.html

Stay prepared by signing up for flood alerts and preparing a flood plan: https://flood-warning-information.service.gov.uk

  

Want to know more?

If you have any questions or want to be added to our mailing list, please contact us at: OxfordScheme@environment-agency.gov.uk

Seacourt again

There’s a story in yesterday’s Oxford Mail on how the Seacourt P&R extension site has been getting on in the recent rather wet weather.

 

 

Oxford today

River levels in Oxford today have not risen as far as had been predicted. So good news so far. The EA is watching things closely for the whole area.

In the case of South Hinksey, the barriers which were delivered there this morning are to be kept in reserve for now. Barriers for other areas remain in reserve at Osney.