Update from the Environment Agency
· Update on LIDAR and flood mapping
· Temporary flood defences.
Tina Donaldson from the EA gave Members a presentation on Temporary Flood Barriers (TFB) which included the following key points:
Ø Tina Donaldson’s team were rolling out TFB plans and her main role in that was in communicating those plans to Local Authorities (LAs), Parish Councils and local communities.
Ø The TFB were a national project which was started following a major flooding event in 2015.
Ø The EA looked at the situation from a national perspective and decided TFB were the way forward.
Ø There were 150 locations with 40 metres of TFB which were backed up with pumps nationally.
Ø The TFB would be stored in seven hubs across the country.
Ø Eddie Stobbart held the contract to deliver the TFB within 12 hours of notification.
Ø The nearest hub for the local area was in Sunbury.
Ø There were five TFB locations identified in RBWM which were:
o Old Windsor
o Windsor, Clewer
Ø Flood barriers were one metre in height and consisted of a metal A-frame.
Ø 100 operatives could erect 100 metres of barrier and then it they would be covered with tarpaulin.
Ø The barriers had to be able to protect more than five properties from a one in 30 year flood.
Ø The TFB had to ensure they did not increase the impact of flooding elsewhere.
Ø The TFB also had to ensure they would not encircle and therefore, isolate the community they were meant to protect from additional support.
Ø There were three potential triggers that would mobilise the TFB which were river levels, forecasts and modelling.
Ø The EA worked with the Met Office and checked gauges on the river. They also used in-house mapping and forecasting teams that knew the area.
Ø Stage one was to consider if the TFBs should be deployed. That would be before any flood alert or flood warning was issued by three or four days.
Ø The second stage was to mobilise and send the TFBs to site.
Ø The final stage was to deploy and erect them in their chosen locations.
Ø Any decisions to deploy would be made in conjunction with a Local Resilience Forum
Ø The alignments of where the barriers would be placed was constantly under review and subject to change. The EA could not guarantee to erect a flood barrier as it was not just an EA decision.
Ø If there was a wide scale flood event, it would be a difficult decision to make as to whether to deploy, or not.
Ø Surrey Resilience Forum did an exercise to look at what locations they could erect TFBs and that showed how difficult it was to place them.
Cllr Beer asked who represented the RBWM on the Local Resilience Forum. Simon Lavin, Flood Risk Manager confirmed Carolyn Richardson was the RBWM representative as part of a shared service with other LAs.
Ø In order to facilitate deployment, it was necessary for the following to take place:
o Enabling works
o Land agreements
o Consultation and engagement
o Deployment of reviews
o Detrimental modelling
Ø the above included clearing vegetation, installing gates, negotiating with land owners to gain access, and lots of modelling would be done to ensure aligning was done accurately.
o To protect homes from Bisham Brook, the barriers would protect approximately 15 homes.
o The EA had spoken to the Parish Council and the owner of Town Farm – those residents would need to be made aware of the situation.
o It was not possible to erect the TFBs by the five houses that flooded from the river so, sand bagging would take place instead.
o Residents needed to be aware of access issues for residents when TFBs were in place.
o The EA were hoping to reduce flooding to 200 homes but, that would have taken up too much of the flood plain. The EA were now looking for a road alignment, which did not reduce the risk to as many houses. More modelling was still to be done to produce the best solution that would protect the most properties.
o No enabling works had been done at that point and the modelling needed to be completed by the end of December 2018.
o The EA would discuss with the council and residents the alignment as some houses would not be protected as the revised alignment did not protect as many houses.
Councillor Lenton stated wherever the EA placed the TFBs, it would create flooding elsewhere. Tina Donaldson responded that the EA needed to assess how bad that would be or, if it makes it so much worse. She also confirmed that a road alignment would block roads and some access by vehicles and that residents would need to be made aware.
Councillor Beer stated if the road alignment was along a residential road, there would be gullys and the water would bubble up through there and cause flooding. Tina Donaldson responded sandbags would be put around the gullys and pumps would be used to pump any water away.
Councillor Lenton asked if tears to the tarpaulin could be repaired. Tina Donaldson confirmed that the barriers had been used elsewhere and had not teared and had performed satisfactorily.
o Modelling had showed water was still finding a way in so the EA was still working on modelling for that area.
o A gate had been installed at the Thames Water inlet to enable a barrier to be erected.
Ian Thompson stated there was a wall down by South Lea Road and it was starting to crumble. Sandbags would be required to hold the wall up therefore, if using the TFBs, the wall might not hold up and might break away. He added it did not look practical because if the TFB was put the other side of the wall, it would have to be higher than the wall to stop the water. Tina Donaldson responded that the barriers followed a road alignment so it should not impact the wall. Ian Thompson stated the height was relevant to the flooding event in 2014. The proposal was not practical as the water was higher than the wall in 2014. Tina Donaldson said it would not cross the water inlet and the barrier would not go along that wall. Ian Thompson added there were houses at a lower level there, if there was any flow of water, it would be able to go around the TFB and would put the whole of Datchet at risk.
Ian Thompson added the Parish Council had a proposal, they intended to try and restore the original protection bund to meet up with the woolacombe bund. It would be ideal if a gap could be set up adjacent to the river on a concrete base. He said the Parish Council were looking at when the RTS would be up and running, the enablement works would need to include installing a bund. However, as they did not know what was happening with the RTS, he proposed they reinstate the bund that used to be there. Ian Thompson concluded that the Parish Council wanted support for the idea from the Borough and the EA. He requested the idea be looked at by a structural engineer; when the RTS started, it would be a part of a channel so the works should be started now.
Tina Donaldson stated from a TFB point of view, the EA would confer with the Parishes when the modelling was completed and would ask if the proposals were good enough.
Tina Donaldson confirmed that 230 houses would be protected if the EA got the modelling right; there would also be a traffic management plan in place.
Ø Old Windsor and Windsor Clewer
o Both areas were similar
o At a one in 30 year flood event, TFB were not needed at that level of flooding.
o The EA had developed a plan but it was being kept on a shelf.
o There was no risk to properties at a one in 30 year flood event but the TFB would be deployed during greater flooding incidents.
Simon Lavin, Flood Risk Manager stated there were options to put pumps in to pump flood water back to the Thames. There was an issue with water coming in under the bund. Tina Donaldson responded that was not at the top of the list as it was not needed at that level of flooding. She confirmed that Old Windsor and Windsor Clewer were second category areas. Temporary barriers were not intended to be used for higher levels of flooding.
Councillor Beer asked if there would be sufficient resources available if Old Windsor moved up a category during flooding. Tina Donaldson said it would depend on national resources such as military deployment. The EA only had a certain level of staff so the issues were around the resources to deal with a flooding event. Councillor Beer commented by resources, Tina Donaldson meant that some properties would not be protected. The Flood Risk Manager stated TFB kits would be deployed at signs of earlier risk and once in place, they would stay there. Tina Donaldson confirmed tributaries would probably receive TFB first but, it all depended on forecasts, the decision made would be multi-agency and would be very difficult decision to make. The agencies that would be making the decisions during the deployment of resources would include the police, fire service, councils and the EA. Harry Clasper stated Datchet and Windsor had significant man power due to the military being based in Windsor so that should not be an issue.
Ø The next steps:
o There would be more communications and engagement with communities, the EA wanted parish councils and the Council to help share information.
o Establish and agree the best method to tell the community if a TFB was going to be deployed before a flood event.
o A traffic management plan was to be produced in the event of the TFBs being deployed.
Martin Coker stated some Parishes had flood hubs that could help with communicating plans to residents and businesses. Tina Donaldson said the EA would use those to cascade information. She also confirmed that Bisham was ready in the event of a flood, Datchet was almost ready. She was not sure if Wraysbury was ready yet as modelling had not been completed yet.
Ian Thompson stated he had accurate flood plans from the flood level in 2014. The defences would not work if there was a similar event to that of 2014. He added his area did not have the defences it needed, flood defences needed to be improved. Brianne Vally from the EA stated the EA would take his comments on board.
Councillor Kellaway stated each TFB unit protected approximately five houses and then they linked together. Tina Donaldson responded that each location where the defences would be deployed needed to protect a minimum of five houses to be considered for deployment. Brianne Vally responded if something similar was being done in Marlow that the EA had not been able to come up with a flood scheme from Thames flooding and that it was under review. However, Marlow would not make Bisham flooding worse.
Harry Clasper said timescales were very fuzzy; it was flood season now. He asked the EA to return to all five areas affected with something more substantial. Tina Donaldson responded that Brianne Vally’s team were carrying out modelling and the EA used a further two consultants. Flood modelling was a very slow process and she understood the frustration. Brianne Vally commented she was working to get the most accurate data and evidence.
v Action – The EA to return to the Flood Liaison Group with an update on the modelling work and TFB information as soon as possible.
Brianne Vally then went on to provide Members with an update on LIDOR and Flood Mapping. The main key points of the update were as follows:
Ø One concern was around historical flood mapping. For planning purposes, someone had requested historical layer flood mapping from 2013/14. It had been challenged several times so that layer would be removed.
Ø Assessment using LIDOR had been carried out, but there was no timescale to provide a more defined outline.
Ø Brianne Vally was aware of Parishes having very detailed maps and she understood the EA had had that information for three years but, it did not impact any planning. The flooding event in 1947 was equal to or bigger than that of 2014.
Ø The EA needed to locate resources to overlay aerial mapping for 2014
Ian Thompson stated the police supplied aerial footage of the flooding that took place in 2014 and he had it at home, he had issued the footage to the EA. Councillor Kellaway stated it was very important as the Borough was also in the process of adopting a Borough Local Plan. Brianne Vally stated she had been working with the Borough to supply information that was the best information available.
Brianne had received an information request regarding Heathrow expansion. Councillor Beer had raised comments about Heathrow needed to do some joined up thinking regarding the River Thames Scheme (RTS) and Heathrow expansion. She added at present it was at high level consultation so she had no more information to provide. Councillor Beer responded the Borough was in between two stages of a local minerals plan which was under review. It was not only an EA concern, there were sewer works there which served Windsor and the site would be overloaded. There had been no consideration for the thousands of homes being built; so the site should be preserved for sewage and not gravel extraction for Heathrow.
Ian Thompson stated there were areas in Datchet of great concern if flood water was allowed to get through, it would cause devastation similar to that in 2014. The Parish Council wanted a permanent solution to holding back water under the arch; there was a pumping station nearby, so that would be recirculating the same water. A stop needed to be installed and it needed to be looked at by a structural engineer and Network Rail. The Flood Risk Manager stated if it was permanently blocked, water would accumulate on the Pococks Lane side and water would not be able to get out. Ian Thompson responded it needed a stop valve so that when water dropped on the golf course, the valve could be opened and release the water. Brianne Vally confirmed she had spoken to Scott Salmon who confirmed when this happened, sand bags were placed. Eton Wick bund had collapsed but it had now been reinstated so would provide the level of protection required after 2014. Ian Thompson explained the design could not carry out what it was intending. The Flood Risk Manager confirmed flood water went over the Eton bund in 2014 and water would go over it again during a major flood event. Ian Thompson said he was aware of that as he was there putting sandbags on top of the wall but, the wall started to crack. Three feet of the wall had given way. Brianne Vally replied as part of the River Thames Scheme, a number of studies took place that showed areas that would not be protected, so the EA was looking at other ways to protect communities. Nine locations would have more work carried out but none of them were in Datchet. The EA now needed to go over the evidence. Ian Thompson’s idea to protect the area needed to be put forward and she would like to work with him on that. Councillor Kellaway asked if the Borough’s capital budget could help. The Flood Risk Manager said any projects would need to go through the commissioning team. Harry Clasper explained the issues had been around a long time; he did not know if the EA had accepted or rejected the ideas and there were six of seven schemes going on, but the situation remained uncertain on them. Brianne Vally responded there were a number of schemes that had been mentioned or suggested but, the EA did not want to say no, so they were looking at ways to secure funding, and how many houses would be protected. But the rules might change. A lot of work was ongoing to get funding for the River Thames Scheme with resources focused on the River Thames Scheme. She accepted there was a lot of uncertainty but, she committed to redoing assessments and sharing information and would access any other ways to secure funding to try and implement ideas. Ian Thompson stated there needed to be something in place now, it could not continue to remain exposed in that way. The Chairman stated there was no point coming to the Flood Liaison Group meetings if nothing changed. He felt strongly that the Council had to deal with issues and put projects into the capital budget and get them moving. Brianne Vally replied the EA would review evidence from the study that was released the previous week and let the Forum know which projects failed. Councillor Beer requested a list of possible funding options that might be available to the Council and Brianne Vally confirmed she would find one and get it circulated.
v Action – The EA to circulate a list of possible funding options for capital projects that the Council could apply for.