Flood modelling works
Our flood modelling specialists HR Wallingford have updated the existing Llandudno flood model to understand how the town may be impacted by coastal flooding. New flooding predictions for North Shore and West Shore give us updated information on how flooding may change over time due to climate change, with rises to sea levels and increased frequency of large waves and storms.
The data has been generated for these timeframes:
- Year 2040 (20 years' time)
- Year 2070 (50 years' time)
- Year 2122 (100 years' time)
The modelling predictions of flooding are for two scenarios:
- 'Business as usual' - where the current flood defences are maintained as normal
- 'Walkaway' - a hypothetical scenario where the current flood defences are not maintained and fall into disrepair
‘Flood risk’ is the likelihood of a flood occurring. We calculate this as the chance that a location will flood in any one year.
So, if a location has a 1% chance of flooding each year, there is a 1 in 100 chance of flooding in any year. This doesn’t mean that if a location floods one year, it will not flood for the next 99 years. It also doesn’t mean if it hasn’t flooded for 99 years, it will flood this year.
The lower the percentage, the less chance there is of flooding in any one year. The higher the percentage then the more chance there is of flooding in any one year. This chance is always there - this year, next year and in the future.
Flooding can be caused by other sources which are not shown on these maps - such as sewers or local drains.
The maps indicate risk to a general area, not to individual properties.
Image 1: North Shore - Walkaway compared with business as usual in the 2% chance of flooding each year (1 in 50 years) scenario
This image compares two predictions of flooding in Llandudno from the North Shore: if the current flood defences are not maintained and fall into disrepair (walkaway) and, if the current flood defences are maintained as normal (business as usual).
The image shows that the current flood defences on North Shore should prevent widespread flooding in a 1 in 50 year storm - but there are a few areas where water could come over the top of the defences.
Image 2: North Shore - Walkaway compared with business as usual in the 0.5% chance of flooding each year (1 in 200 years) scenario
This image shows that the current flood defences should prevent widespread flooding in a less likely, but bigger and more severe storm. But there are some areas where water could come over the top of the defences especially in the east near the new RNLI Station.
Image 3: West Shore - Walkaway compared with business as usual in the 2% chance of flooding each year (1 in 50 years) scenario
This image compares two predictions of the extent of flooding in Llandudno from the West Shore: if the current flood defences are not maintained and fall into disrepair (walkaway) and if the current flood defences are maintained as normal (business as usual).
The image shows that the current flood defences should prevent some flooding in a 1 in 50 year storm. But there are some areas (particularly around Dale Road car park) where water could come over the top of the defences and flow into residential areas.
Image 4: West Shore - Walkaway compared with business as usual in the 0.5% chance of flooding each year (1 in 200 years) scenario
The image shows that the current flood defences may not be substantial enough to prevent flooding on nearby residential areas in a less likely, but bigger and more severe storm.
Using this new flood risk data, we will finalise our proposals for improvements to increase the existing flood defence provision. This will include carrying out site investigations on North Shore from October 2023 to assist with the design of improvements.
We will hold a public information event in 2024 for residents and businesses.
We aim to be ready to start work on building the improved flood defences in 2024.
We have secured funding from the Coastal Risk Management Programme (CRMP) to pay for a full business case and detailed design.
The Cabinet has decided to accept funding from the Coastal Risk Management Programme (CRMP) to continue with the non-sand option for North Shore coastal flood risk reduction, and at West Shore.
Welsh Government’s Flood and Coastal Erosion Risk Management branch has told us that the option for putting sand on North Shore cannot be funded by the Coastal Risk Management Programme (CRMP).
This programme is targeted at reducing coastal flood risk and they do not believe the sand option provides any extra coastal defence benefits. They consider that the £23.9m cost for the sand option is not justifiable when the £6.7m option of raising the promenade wall would have the same coastal defence benefit.
Welsh Government stated that they appreciated the strong local desire for a sand beach on a specific part of North Shore, but that the CRMP programme is not the appropriate way to achieve this at such a significantly increased cost.
Councillors in the Scrutiny Committee have agreed, as a priority, to lobby Welsh Government ministers for Economy and Climate Change and the UK Government to seek funding.
The outline business case has been approved by Welsh Government. We are now working on the detail needed for the full business case, advancing the concept designs for the options in the outline business case. We will be working on ground investigations and holding a public consultation later this year.
We have submitted the final outline business case to Welsh Government for technical review and consideration against programme objectives. The next step will be detailed design work of the scheme, which will involve public consultation.
The work done to date on this coastal defence improvement scheme has been funded by Welsh Government through its Coastal Risk Management Programme (CRMP). We will be applying for Welsh Government funding for future stages, with some of the funding coming from Conwy County Borough Council.
On 8 June 2021, the Cabinet reviewed the draft outline business case and shortlisted options. Cabinet identified their preferred option for North Shore was to remove the cobble bank between Vaughan Street and Children’s Corner and replace it with sand.
Llandudno Coastal Forum, working with Conwy County Borough Council and its consultants, organised a public drop-in session at the Victoria Centre in Llandudno on Friday 27 and Saturday 28 July 2019. Residents and visitors viewed the shortlisted options for managing Llandudno’s beaches and gave their comments. View the Llandudno Flood Defence Improvement Boards. Comments were also submitted via our website.
We have compiled the comments we received into a report to accompany the outline business case.