Llanfair Talhaiarn flood risk management

Latest update (August 2021) on actions following the February 2020 flooding

Due to the coronavirus pandemic, we have been unable to hold a drop-in session in Llanfair Talhaiarn to discuss flooding issues.

In the meantime, we are in regular contact with Llanfair Talhaiarn community council and provide regular updates on our work to help reduce flood risk in the village.

We hope this latest update helps keep you informed in these challenging times, before we can return to discuss matters with you face-to-face once again.

Please forward your comments or any questions via email to: Flood.Risk.Llanfairtalhaiarn@naturalresourceswales.gov.uk

Work continues on many fronts... here’s the latest situation

The new top section of the Nant Barrog Water Street culvert in the village, completed in late 2018, is performing well, allowing the culvert to carry much more water safely at times of high flow.

However, we must remember that even the improved culvert has a capacity limit and there will always be a possibility of it being overwhelmed in a major flood event - as happened during Storm Ciara in 2020.

Blockages at the mouth of the culvert is also a risk we have addressed. Following a review, we made changes to the existing screen last winter, which significantly reduce the possibility of blockage. We have been monitoring the adapted screen and are pleased to report that the changes have had a positive impact.

Phase 2 works for Llanfair Talhaiarn’s flood risk management scheme will involve improving access to the screen and simplifying clearance operations for NRW staff. Walls will also be built at Capel Soar, upstream of the culvert inlet, to keep more water in the channel to make full use of the new culvert’s increased overall capacity.

Due to safety issues and risks associated with not being able to complete Phase 2 works before the winter months, it has been decided that it will be safer to undertake these in Spring 2022.

We are fully aware that this will be disappointing to local people. However, we want to reassure everyone that we are fully committed to making sure the current adapted screen, which is performing well, is inspected regularly and monitored carefully as part of managing the village’s flood risk.

Phase 2 works could not start earlier due to design changes to maximise benefits, work to ensure legal compliance and gain all permissions, consents and development certificates and, of course, covid. But we are now able to ensure the work starts in April 2022, when it is safe to do so.

In the meantime, we continue to work on other important aspects of flood risk management for the village, which are listed below:

We have made improvements to the camera, which contributes to monitoring the river, upstream of the culvert. An additional camera has been installed at the gravel trap area. We are also considering installing additional cameras on the system.
Nant Barrog river level data continues to be monitored. Whilst useful for our operations teams, it will not be added to River Levels Online until we are confident that the monitoring station provides a good and consistent standard of readings. This may take 12-24 months in line with other new monitoring stations.
A review of property protection to homeowners at risk of flooding (such as flood boards) is being completed and we can now review the findings and consider applying for funding to deliver works on the ground.
We are exploring options for providing a full Flood Warning Service on Nant Barrog for Llanfair Talhaiarn. However, this is a complex issue due to the nature of the catchment/availability of data.
We are working with the volunteer Flood Warden Group to update Llanfair Talhaiarn’s Community Flood Plan, including sharing information to residents about the early warning service. We will provide support to the Group with any test events/preparatory work that will be undertaken later this year, ahead of the Winter.
There are 54 properties at risk of flooding, but only 23 have registered for the Early Warning Service. If you haven’t registered for this service, please contact Gwenno Talfryn on 07811023377.
We continue to work on the potential for natural flood management works. This means using natural solutions, such as planting trees or leaky dams, to help reduce the flow of the water upstream. Coed Cymru (CC) has started a project, fencing and planting trees in upstream areas. NRW will continue to work with Coed Cymru whilst progressing our own investigation and continuing to look if storing water upstream can play a part. It is likely that installing structures in the upper river, to slow the flow of water, will be one of the key options to consider and that work will progress in 2022.
A review of the Elwy flood embankment (School Lane area flooding) has been completed and we are reviewing the findings.
We are working closely with the community council to develop a Catchment Wide Flood Partnership Group for the Nant Barrog, to look at the wider flooding issues impacting on the community and to put in place ways of managing these issues into the future.
We have reviewed the Elwy Weir’s impact on flood risk and the findings indicate minimal impact.
We are reviewing the performance of the coarse debris screen (known as the tree catcher) and have asked our designer to consider improvements. These will hopefully be delivered next year in parallel with the re-programmed Phase 2 works.
Land between the culvert inlet and the tree catcher is being cleared to reduce the risk of blockage. This will hopefully be subject to a management plan with landowners to reduce blockage risk in the future.

We must remember that as climate change intensifies, we will experience more extreme weather events, including intense wet periods such as those experienced last winter. This makes flood risk management an increasing challenge for the years ahead.

You will also find answers to lots of questions here.

Enquiries: Flood.Risk.Llanfairtalhaiarn@naturalresourceswales.gov.uk

You can also discuss matters with:

Conwy County Borough Councillor Ifor Lloyd cllr.ifor.glyn.lloyd@conwy.gov.uk

Senior Flood Warden, Julie Elliott
Phone: 01745 720 255 or 07789 965. Email: j.crossan55@btinternet.com

Assistant Flood Warden, Karen Minor
Phone: 01745 720 513 or 07919 458 835 Email:karenminor3@yahoo.co.uk

Update following Storm Christoph, 20 January 2021

As with all storm events, NRW is now reviewing what happened before, during and after Storm Christoph.

Initial information indicates that it was a significant weather event with very high rainfall. There was a real flooding risk to the community of Llanfair Talhaiarn again.

NRW officers were on site during the event, monitoring the situation and on hand to deal with issues as required.

The changes to Capel Soar screen, completed in 2019, had a positive impact on the flow of water down the culvert, allowing small debris to pass through, and reducing the risk of blockages.

We will continue to monitor this before we decide on the long-term design of the screen structure.

We also believe that the work in 2018, which increased the capacity of Water Street culvert, played its part in carrying the water faster through the culvert.

The upstream coarse screen was partially blocked with woodland debris, as expected and designed. Gravel was also deposited upstream. We have now cleared this area and will continue to monitor the performance of this screen also.

The flows in the Elwy were very high and we are aware that there was concern about School Lane becoming a flood route as the river came out of bank. This is being investigated.

We are aware of surface water flooding issues that occurred and will assist our colleagues in Conwy County Borough Council to investigate this as required.

Unfortunately, the impact of Storm Christoph demonstrates the challenges of a changing climate and the ongoing risk to the community.

We must remember that as climate change intensifies, we will experience more extreme weather events, including intense wet periods as we are currently experiencing. This makes flood risk management an increasing challenge for the years ahead.

Following Storm Christoph, catchments across north Wales remain wet and very sensitive to rainfall. This means, in the short term, many rivers may respond more quickly in response to small rainfall events.

We hope that the Community Catchment Flood Group, that is being developed, will further enable the community and public bodies to work together to address flooding issues, reduce flooding impact and become more resilient.

NRW is eager to get as much information as possible regarding the Storm Christoph event. If you have any comments or feedback/info/photos of flooding or flood related issues please forward to NRW via: Flood.Risk.Llanfairtalhaiarn@naturalresourceswales.gov.uk

Background (where we were before Storm Ciara March 2020)

November 2012 saw flooding to the village of Llanfair Talhaiarn (TH) when the Nant Barrog, swollen by extreme rainfall, overwhelmed the Water Street culvert and flooded 19 homes and businesses.

This followed previous flooding in the village, during April 2012 along with numerous other reported incidents in the past 50 years.

Based on modelling, the November 2012 flood was estimated to have had a two percent chance of happening in any given year.

But, as evidenced by the frequency of flooding incidents in the village, in 2012 Llanfair TH was actually thought be at risk from floods on the Nant Barrog with a four percent chance of happening in any given year, due to overwhelming the Water Street culvert.

This risk of flooding is exacerbated by blockage of the trash screen, across the inlet of the Water Street culvert.

The River Elwy flows along the northern edge of the village. The November 2012 flood on the Elwy was reported as being between a one percent and two percent chance of happening in any given year. Existing flood defences protected Llanfair TH from further flooding from the Elwy during November 2012 - the village was solely affected by flows on the Nant Barrog.

Developing a flood risk management scheme

Since the 2012 flood events, we've been undertaking work in the village to improve resilience to flood risk and reduce the risk.

In 2016, we completed an appraisal of the flood risk, to assess the flood risk and came up with proposals to further reduce this risk.

The flood risk management scheme improves the capacity of the Water Street culvert.

Once completed, it will also improve the performance of the trash screen and we will investigate options to make improvements upstream to protect the village against flooding.

The flood scheme currently proposed will provide the village with protection of one percent chance of flooding from the Nant Barrog happening in any given year, once completed. It will also mean that the debris screen will be easier to manage and will not be as sensitive to blockage as the existing screen.

The construction of the flood risk management scheme is phased, with Phase 1 completed in January 2019, increasing the capacity of the culvert to being able to carry flows equivalent to 1.33 percent chance of flooding happening in any given year.

Phase 2 is planned for later this year, 2020 subject to obtaining planning and other permissions and review following the 9 February 2020 floods. This has now been postponed to April 2022.

Phase 1 works involved improving a key upstream section of the Nant Barrog Water Street Culvert and The Black Lion Nant Barrog Culvert section. We have removed the old culvert sections at these locations and replaced them with larger sections. We also did work to seal the culvert throughout its length.

NRW is grateful to the residents for their support and understanding throughout Phase 1.

This work improved the capacity of the culvert and it is now able to accommodate increased flows, giving the village a 1.33 percent flood risk in any given year.

There is still a risk posed by the existing debris screen. NRW officers attend the site during high flow/heavy rainfall events but the current screen is difficult to maintain and keep clear of debris.

Phase 2 works will involve improving the existing debris screen arrangement at Capel Soar. A new, additional, wider debris screen is planned. Walls will also be constructed to keep more water within the channel to drive it through the culvert to optimise its capacity. We have considered all options to ensure that we come up with the most suitable and sustainable solution. Construction on this will start in April 2022.

The flood scheme will be supported by work upstream to manage the peak flow of water through the village by using natural flood management methods, by working with partner organisations.

NRW is hoping to work with Coed Cymru to look at natural solutions including planting hedges and creating natural barriers to the flow of the water upstream.

We will hold a further consultation event in the village before the next stage of works.

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