Agenda item

UPDATE FROM THE ENVIRONMENT AGENCY

To receive the above verbal update.

Minutes:

Brianne Vally, Environment Agency, provided and update to the Forum. The Thames catchment received 234% of average rainfall for October 2020. Marsh Lane, Maidenhead, recorded the maximum weekly total of 47mm. River flows increased on all sites since last week (at the time of meeting) and were well above the monthly average for October. Resultantly, catchments were more responsive to rainfall. The Met office long-range forecast predicted settled conditions with outbreaks of rain. In the second half of November 2020, there were predictions for frequent showers effecting the east of the UK.

 

Material was circulated offline regarding the Flood Action Campaign to support the campaign from the 9 to 11 November 2020. The campaign was created to remind people of actions to take before, during and after a flood event and Brianne Vally requested Members to support the campaign. The Chairman asked how parish councils and the borough could support the campaign and the Group was informed that videos could be shared on social media, posters that could be shared with local communities, as well as adding the email signatures to show their support.

 

There had been an initial internal workshop in September 2020 to discuss alternatives to Channel Section 1 for Datchet, Wraysbury and Old Windsor. A report was produced, and the next step was to have further discussions with the Chairman for appropriate resourcing, agree the objectives and measures and the engagement plan. The Chairman said he was waiting for a response from Sarah Haleto schedule a virtually meeting with Chris Joyce, Head of Infrastructure, Sustainability and Economic Growth and Ben Smith, Head of Commissioning – Infrastructure.

 

ACTION: Brianne Vally to contact Sarah Hale to schedule a meeting with the Chairman, Chris Joyce and Ben Smith.

 

The Herts and North London team covered parts of the Wraysbury area was updating some of the lower Colne’s hydraulic modelling that would refine the EA’s understanding of flood risk. This would be shared with the Group once available.

 

Repair work was being undertaken on the Black Potts weir on the Jubilee River following a routine inspection that identified erosion downstream side of the weir. The intention was to return the flood relief channel to an operating condition by Christmas 2020, to coincide with the wetter period between January and March 2021. It was possible that additional works would be carried out in 2021.

 

James Liney, Asset Performance Team Leader, said an underwater survey took place in August 2020 which revealed scouring, causing erosion to the riverbed downstream of Black Potts weir. The issue was further complicated because of the viaducts and the railway above it. The underwater survey showed no damage to the weir and the bed of the weir, and the viaduct was unaffected at present. However, left unattended, erosion could work back up the weir and the viaduct. Emergency contractors were hired through the Environment management framework to set up the site compound in the coming weeks. The Jubilee River would continue to flow at 5 to 10 m3/s. Black Potts weir was the only part of the Jubilee River that was affected.

 

Councillor Larcombe said in 1988, a rail bridge collapsed on that line in Wraysbury. He said the problem of erosion and scouring also occurred downstream of Taplow Mill Leat and downstream of the Taplow control structure where a stilling basin was not placed. He asked why erosion problems were occurring, when the system was only running at two-thirds of its design capacity. James Liney said there were similar size weirs on the River Thames with similar effects. Regular routine and reactive maintenance downstream of the weir along the River Thames were taking place. In 2017, a survey highlighted the potential for the start of deterioration, and it was recommended to undertake an underwater survey following the heavy use of the structure. The follow-up strategy took place in August 2020, which was later than expected due to restrictions following COVID-19.

 

Dick Scarff, Cookham Society, said there were higher flows in 2014 and asked if there were any scouring problems since. James Liney said there were cumulative issues which led to the effect on the riverbed and the structure was 19 years old. He said he would review this.

 

ACTION: James Liney to update Dick Scarff if there was scouring problems since 2014 at Black Potts weir.

 

Councillor Brar said she thought the issues were present since 2014 and asked why the EA was starting work now, as Cookham was at risk of flooding due to the weather. James Liney said the full detail of deterioration of the riverbed was only clear to the EA from August 2020. The 2017 survey highlighted that the riverbed needed to be reviewed after the next heavy rainfall event. The EA was working quickly with the information collected from August 2020, and he said he was unable to comment about the assertion about 2014. Brianne Vally said the other flood alleviation assets part of Maidenhead Eton and Windsor flood alleviation scheme would be operated, which would reduce flood risk in Cookham regardless of status of the Jubilee River.

 

Ian Thompson, Datchet Parish Councillor, said water levels were approaching 21 metres above ordnance datum in 2014. He said that if works were carried out, the flow of water would come back from the Thames River and into and up the Jubilee River. He said it was suggested there was a sweetening flow in the Jubilee River and asked where the water would go and how would it effect the works below the weir, which would be many metres below the surface of the water.

 

Brianne Vally said the contractors designed a modelling simulation to assess the impact of velocities and turbulences on the scouring. The work to be carried out needed the EA’s permission and she believed the detail would be included in the methods of works of the application. Brianne Vally would be able to advise on the mitigation measures then once this was reviewed.

 

Ian Thompson asked if the method statement could be shared with the Datchet parish council so that it could be reviewed, as it effected residents in the area. Brianne Vally said the information that was being shared as part of the Flood Risk Activity permit was in the public domain and could be shared, once the application was finalised and would share the method of work for awareness. She said Datchet would not benefit from the reduction in flood levels when the Jubilee River was or was not operating, and the works would be carried out to ensure local areas would not experience increased flood risk.

 

ACTION: Brianne Vally to share the method of work with Ian Thompson.

 

Cookham Parish Councillor Jane Perry said she was concerned about the effects of the EA’s decision to not dredge some of the local streams that were important in getting water away from properties. Her house was flooded in 2014, and since then, there was a band around a nearby gravel pit to protect the pit from water, which would prevent flood of water across the flood plain. She asked if there were any measures that could be taken that would reduce the risks whilst the Jubilee River was not functioning as it should.

 

Brianne Vally said the flood alleviation assets in Cookham and north Maidenhead would take place as per operating instructions, which would help reduce flood risks. The Chairman said the parish council or Councillor Clark could write to Brianne Vally directly.

 

Ian Thompson said a report was circulated to Members regarding the heavy downfall of rain that caused minor flooding in Datchet due to blockage from weed overgrowth in the Datchet Common Brook. This caused minor damage to some gardens on Penn Road, and he asked if the EA and Thames Water would clear the blockage.

 

Brianne Vally said the Common Brook was not on the maintenance programme and she would raise this with colleagues. She said it was the riparian owners’ responsibility to ensure water flowed naturally and any concerns of obstruction on the natural flow should be removed. The points raised by Ian Thompson would form part of the wider discussion for Old Windsor, Datchet and Wraysbury. She advised for any immediate concerns to be raised through the Incident Communication Service.

 

Denise Kinsella, Thames Water, said this could be raised with the site owners and could be discussed offline. Ian Thompson said he would like the flow to be sped up as slow flow would increase the height of the Common Brook. A flat valve was sought to prevent the water coming into the Brook, which would otherwise put properties at risk. The Chairman said this matter was being progressed by Sue Fox, Principal Commissioning Officer, and would be part of the wider flood alleviation risk discussions by the EA.

 

ACTION: Denise Kinsella to update on the clearance of the Datchet Common Brook blockage.

 

Cookham Parish Councillor Martin Coker, asked for the Battlemead to remain clear, and whilst some wanted to allow flora and fauna to grow, it was important to allow water to flow. The Chairman said this was an appropriate discussion for the Battlemead item for the next meeting.

 

Laura Regazzacci, Secretary of Eton Wick Waterways Group Committee, said a group of 15 group volunteers cleared out weeds due to the lack of assistance from Thames Water, the EA and other bodies. It had become an issue, causing flooding of gardens, cellars and loss of trees due to high levels of output from Slough sewage treatment works and flooding. In 2014, following floods in Slough, an increased output of sewage came into the village. She raised concerns about winter 2020 because of the Jubilee River not operating and the higher levels of water. She wanted to inform Members that the streams were overloaded with water and could be a flooding risk. The Chairman said this was a concern, the source was known, and working closely with Thames Water and the EA was encouraged.