Yaverland Coastal Defence Scheme Information Page

Overview

Welcome to the Yaverland Coastal Defence Scheme Information Page.

Preferred option announced: 18 March 2024

Our latest newsletter can be viewed below.

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A copy of the March 2024 newsletter can be downloaded here. 

Design work to progress on option chosen to refurbish the coastal defences

The coastal defences will continue to reduce the risk of coastal erosion and flooding to the Yaverland and Sandown area for 50 years to come following a decision by Isle of Wight Council on the best way forward. The decision to refurbish the coastal defences was made following review of a series of ground investigative works, financial analysis and flood risk assessments. The public consultation told us that better protection from coastal erosion and flooding is important locally. The scheme will provide over £160 million worth of benefits to people, property and the environment. The project team will now draw up an initial design and establish a construction methodology for the refurbishment work.

A reminder of the short list of options

In November 2023 we were pleased to hold public exhibitions to showcase the short list of options for refurbishing the coastal defences.

We produced the following information for our public exhibitions to help explain what the scheme is about and how we arrived at our short list of options:

Exhibition banner 1 - Introduction

Exhibition Banner 2 - Scheme extent

Exhibition Poster 1 - Survey and Investigations

Exhibition Poster 2 - Constraints and Opportunities

Exhibition Poster 3 - Measures considered

Exhibition Poster 4 - Project objectives and criteria

Exhibition Poster 5 - Short List

The short list of options being considered were:

Option 1: Do Nothing

Option 2: Do Minimum

Option 3: Keep the existing defence level

Option 4: Raise the level of the defence in stages into the future

Option 5: Raise the defence level now

Preferred Option: Option 3 (keep the existing defence level)

Option 3 (Keep the existing defence level) has been chosen by Isle of Wight Council as the preferred way forward following a recommendation made by the Environment Agency.

Option 3 will involve construction works to refurbish the sea wall and timber and concrete groynes. The methodology for refurbishment will be confirmed during the next stage as the team progress with drawing up an initial design. The current thinking is that works to the walls will be constructed using shutters and in-situ pour of concrete 200mm against the face of the existing sea wall. This option will provide a quality finish. Temporary works such as sheet piling will be required along the section of wall and groyne being worked on to provide a safe and dry working corridor.

The defence level will be kept at the existing level. No raising of the existing defence height will be made over the next 50 years. As part of the refurbishment project, we will include works which strengthen the foundations of the seawall with the foresight that a decision to raise the height of the seawall may be a viable option in 50 years’ time.

How was the preferred option selected?

An overview of the options appraisal process at Outline Business Case stage is presented in the poster below:

Exhibition Banner 2 - Scheme extent

Summary of public consultation responses

We received 45 responses in total. Of the 45 responses, 35 people gave their permission for us to publish their response.

Summary of key findings from the consultation responses:

• No one favoured the do nothing or do minimal option (short list Option 1 and Option 2). Respondents told us that better protection from coastal erosion and flooding is a priority. 
• Option 5 was the most favourable option to raise the defences now to address future sea level rise. A total of 32 of the 35 respondents agreed or strongly agreed with taking option 5 forward. Respondents told us that there is an interest locally in raising the height of the coastal defences to reduce the risk to Yaverland and Sandown from rising sea level both now and in the future.

The full report summarising the responses to the public consultation can be viewed here.

The flood risk assessments and financial analysis were being progressed at the same time as public consultation. This information is now available and presented below.

What did our investigation work show?

Updated flood risk assessment

Flood modelling uses predicted river flows, rainfall, and coastal levels combined with topographic data and flow equations to generate flood risk information (such as depth, velocity, flood levels, and hazards). Our team of specialists updated the coastal flood modelling for Yaverland to ensure it uses the latest information and software available.

The main coastal threat to Yaverland is failure of the sea defences due to their current poor condition. Our latest modelling predicts that failure of the coastal defences would adversely impact 138 residential properties and 136 businesses. The below map shows the anticipated flood extent in the event of defences failing.

Preventing this scenario can be achieved through either Option 3, Option 4 or Option 5. Increasing the height of the coastal defences does not provide any additional erosion protection over Option 3, it only provides a greater level of protection against flooding associated with waves overtopping the seawall.

Modelling results tell us that the risk of flooding from wave overtopping is low given the existing height of the defences and raised floor levels of properties. Modelling suggests that 11 residential and 16 non-residential properties at Yaverland would remain at risk of internal flooding from overtopping after completion of Option 3.

Financial analysis

Option 3 provides over £160 million worth of benefits to people, property and the environment. The additional benefits associated with Option 4 and Option 5 are not as great. The figure below shows the cost to construct Option 3 is significantly less compared with Option 4 and Option 5. Increasing the height of the sea wall almost doubles the cost of the scheme. The public consultation told us that there is interest locally in raising the height of the existing defences however the funding shortfall of £6.4million and over £13million for Option 4 and Option 5 respectively makes these unviable options for Isle of Wight Council to take forward.

Information on Flood and Coastal Erosion Risk Management schemes are funded can be found here: https://thefloodhub.co.uk/frms-funding-and-delivery/

How will the shortfall in funding for the preferred option be addressed?

As a competent authority under Habitat Regulations the Environment Agency must have regard for the protection of the designated freshwater habitat of Brading Marshes, and can therefore apply for funding set aside to protect designated habitat. This funding will only cover the costs to close a funding gap for the lowest cost option for achieving habitat protection. This is Option 3 which is the most economically viable way of protecting Brading Marshes.

The Environment Agency submitted a business case to Southern Water seeking a contribution towards the scheme as the water treatment works in Sandown will benefit from better protection from flooding from the sea. This bid has been included in Southern Water’s submission to The Water Services Regulation Authority, or Ofwat. This bid will not be determined until December 2024.

A funding strategy will be produced during the Full Business Case stage in 2025. Project costs are expected to change following more detailed costings from our contractor.

Ground investigative work

Our contractors drilled boreholes at various points on the sea wall at Culver Parade using specialist equipment to retrieve a core which was sent to the laboratory for analysis. Machine excavated trenches located at intervals along the sea wall and next to the groynes were also dug.

This work helped to increase our understanding of the existing structures and will help us plan the refurbishment work. The key findings are:

• A new area of Dinosaur Footprint was discovered during the work. The new footprints make it clear that the land on which the dinosaurs walked is likely to stretch the whole length of Yaverland beach. A palaeontologist will be on hand to keep a watchful eye over the construction work.
• A total of nine concrete cores were extracted at strategic locations along the concrete sea wall. The cores showed that the Wessex Formation is present as bedrock across the whole site. At the western end of the site, the Wessex Formation is reported to alternate between a Clay and a Mudstone of various degrees of weathering. The Wessex Formation is notably multicoloured, in places mottled brown and purple, reddish brown, greenish grey and bluish grey. Its strength varies with the degree of weathering from a soft Clay to a very weak Mudstone, with bands of sand and Sandstone which is highly erodible. The presence of a stepped revetment around Yaverland car park demonstrates that erosion risk through scour at the toe of the sea wall has been a concern in the past. The soft erodible bedrock will need to be a consideration as the team draw up the design.
• The sea walls are much thinner than modern engineering standards. This tells us that works to the foundations will be needed as part of the refurbishment work.
• Borehole cores extracted from the ground have been donated to the British Geological Society. Their data sets provided useful information for our projects, and we hope our contribution will help others in the future.

The below image shows two of the borehole cores extracted from the ground and stored in their wooden containers: 

Coastal processes assessment

• The historic trends in beach profile from 2004 to 2020 were reviewed. The min/max envelope in the image above shows the beach level overall remains relatively stable across the survey period.
• Short term fluctuations are observed and indicate seasonal changes. Photographic records taken by Swim the Wight provide supporting evidence of this.

• The overall stable condition is attributed to the constant nourishment of sediment received from the south-north net sediment transport rate of 25,000m3/year on average.
• Satellite imagery captured evidence of North-South longshore sediment transport in 2005, 2014, and 2015. This is opposite to the predominant direction.
• Accumulation of sediment on the northern side of most of the groynes in Yaverland indicates the groynes are functioning well.
• Past storm events have caused beach levels to lower by up to 1metre in front of the sea walls.  
• One of the major physical impacts of a rise in sea level includes erosion of beaches. Our coastal processes assessment shows that beach levels are expected to lower by 0.5m by 2040 and up to 3m by 2125.  It is expected that the toe of the sea wall will have sufficient beach cover to protect it from erosion for the next 50 years. After this point, works to prevent scour at the toe of the sea wall may be needed.

Why was the preferred option selected?

The financial assessment compared the benefits and costs to identify the impact of each option overall. The benefits to the community of progressing Option 3 (the preferred option) outweigh the costs. The work will bring over £160 million worth of benefits to the community, the local infrastructure, and the local environment.

The figure below summarises the Short List appraisal for those options deemed to qualify for consideration as the Preferred Option (Options 3, 4 & 5).

The ranking of the options is based on:

• The criteria grouped by PESTLE (Political, Economic, Social, Technical, Legal, Environmental).
• The criteria grouped by Objectives.
• Economic, Financial, and Carbon ranking

A PESTLE analysis studies the key external factors (Political, Economic, Social, Technal, Legal and Environmental) that influence an organisation or environment. It can be used in a range of different scenarios, and can guide people and professionals in strategic decision-making.

Option 3 meets all project objectives, scores highly for PESTLE criteria and scores highly for economic, financial and carbon ranking.

Option 3 also has the longest duration of benefits (50 years) when compared to the other options (20 years). Other than the usual maintenance for Isle of Wight Council and the Environment Agency, no interim works are expected in the 50 years of the scheme.

Why is the height of the sea wall not being increased?

The flood risk assessment shows that the risk of internal property flooding from waves overtopping the existing sea wall is low given the height of the existing wall and raised floor levels of properties. Only a small number of properties would remain at risk of internal flooding from waves overtopping the sea wall after the refurbishment work is complete. Our modelling estimates that 11 homes and 16 businesses would remain at risk of internal property flooding from a tidal flooding event with a 0.5% annual probability (1 in 200 chance each year).  This is compared to 138 homes and 136 businesses at risk of internal flooding from the sea if we did nothing.

The financial analysis suggests that other measures such as Property Flood Resilience (PFR) measures are a more cost-effective method of reducing the risk of internal flooding to the 11 homes and 16 businesses which remain at risk after the scheme is constructed. This opportunity will be explored as part of the next phase of work on the scheme. PFR measures can include flood boards, air brick covers, non-return valves and pumps, as well as work to ensure that the fabric of the property is sound. More information about PFR can be found here: https://bluepages.org.uk/

We can never remove the risk of flooding entirely. Our flood risk assessment shows that if the height of the sea wall was to be increased, there would still be a risk of wave overtopping and associated internal property flooding. The number of properties that would remain at risk of internal flooding today if Option 4 and Option 5 were to be implemented are shown in the table below.  

The results of the financial analysis have shown that the additional scheme benefits from raising the height of the sea wall do not outweigh the additional scheme costs. Increasing the height of the sea wall almost doubles the cost of the scheme. The shortfall in funding makes the option to raise the height of the sea wall an unviable option for Isle of Wight Council to take forward.

Where does this leave us in the future with sea level rise?

The risk of flooding from the sea over the next 100 years with 1 metre of sea level rise was modelled to improve our understanding of how the risk of flooding in the area may change in the future. It is estimated that without increasing the height of the sea wall, 164 homes and 142 businesses would be at risk of internal flooding from the sea by the year 2121. Raising the height of the sea wall would still leave 101 homes and 103 businesses at risk of internal property flooding from the sea by the year 2121.

As part of the refurbishment project, we will include works which strengthen the foundations of the seawall with the foresight that a decision to raise the height of the seawall may be a viable option in 50 years’ time.

Previous updates

Our latest newsletter can be viewed here:

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A copy of our latest newsletter can be downloaded here.

If you require this in another format please don't hesitate to contact us at IOW_FDschemes@environment-agency.gov.uk

The Environment Agency have created this page to provide easy access to information on the Yaverland project, one of four priority coastal defence projects on the Isle of Wight. The Environment Agency will be updating this site as the project progresses, so please keep checking for what’s new.

Please get in touch if you need any of the documents on this site sent to you in a different format. We would be happy to help.

For information about other coastal defence projects on the Isle of Wight see here.

The Sandown Bay coastal frontage is a popular tourist and amenity area with its long sandy beach, esplanade and attractions. This project aims to address the flood risk and coastal erosion challenges facing this stretch of coastline.

This work aims to enhance the seafront for future generations and assist regeneration, whilst reducing flood risk to the community and preserving the area’s tourism and heritage value. Additionally, the project will explore longer term flood and erosion risk management options and make recommendations for a sustainable coastline for future generations.

What if we do nothing? More Information

The existing sea wall embankment is occasionally overtopped by waves during stormy conditions, causing localised flooding. This can be seen in the photos below, taken in 2015.

The condition of the sea wall and groynes between Yaverland car park and Sandown (Culver Parade) varies. Some sections of the sea wall are in a very good condition, and are expected to offer sufficient protection for many years to come. Other sections are in need of repair. The groynes may be near the end of their useful life and in need of significant repair or replacement. The photos below show some of the deteriorating structures.

If the Environment Agency take no action, these poorer sections are at risk of failure, which would lead to a breach in the sea wall and flooding of the low lying land including properties and infrastructure in Yaverland and Sandown bordering the Eastern Yar valley. The map below shows in red the section of sea wall that the Environment Agency is looking to refurbish. The area in blue is land that would have a 0.5% or greater annual probability of sea flooding if the wall was not in place.  

The predicted 0.5% annual probability tidal flood event with no defences in place

Frequently asked questions can be viewed here.

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