Ventnor Coastal Protection and Slope Stabilisation Scheme Information Page

Project Update: Coastal Defence Works

The first phase of the trial dewatering scheme, conducted above the Western Cliffs, was successfully completed in mid-March. While initial findings indicate some technical challenges, the potential of groundwater management as a method to extend the lifespan of our coastal defences is still being explored. Ongoing groundwater monitoring in the area will help provide a clearer picture. Once the full assessment is complete, the results will be peer-reviewed by Jacobs Consulting, the Isle of Wight Councils landslide consultants, to ensure all our conclusions are well-founded and reliable. 

In addition, ground investigation works at Wheelers Bay and Easter Esplanade were finalised in late May. Core samples from these areas have been sent for laboratory analysis, with results expected by mid-October. The data from these investigations will be combined with previous visual asset inspections and the results from our specialised coastal model. For the remainder of this year we will be analysing all of this information to identify technically viable solutions for the management of coastal erosion. We aim to share the findings and present solutions that are technically and environmentally sound, cost-effective, and feasible by Spring 2025.

The trial dewatering scheme (Phase 1), undertaken above the Western Cliffs, was completed in mid-March. The initial findings suggest that there are technical challenges associated with the theory that groundwater management can be used as a  viable option for extending the life of the coastal defences. We are currently monitoring the ground water level and awaiting more further lab results/analysis. Once a full assessment has concluded, anticipated to be completed by September 2024, we will share the findings.

Our coastal defence  ground investigation works in Wheelers Bay  were completed  in late March. We have 2 further boreholes to undertake, 1 close to and 1 within the perimeter  of the ongoing urgent works, fronting Ventnor Eastern Cliffs. The works will be complete before the end of May.  The core samples will undergo lab analysis, with the results/report expected in August 2024.

The information gathered during the above ground investigations will be combined with earlier completed visual asset inspections and the outputs of the bespoke coastal model (expected August 2024).  We will then share the information we have gathered and present viable options which are technically and environmentally sound, and affordable and buildable.

The aim of the viable options will have to show how they can successfully mitigate significant reactivation of the relic landslide complex, on which Ventnor and the surrounding villages has been built.  

Ground penetrating radar surveys (GPR Surveys)

GPR surveys are a non-intrusive investigation approach to understand the sea defence dimensions, voiding and location of services within the defences. This is useful information that will inform the next phase of investigative works which is broadly known as Ground Investigations. Unfortunately, the GPR results were inconclusive, as is often the case when surveying reinforced concrete due to the presence of steel which disrupts the radar.

Visual Asset Inspection

To assess the quality of the Ventnor Coastal defences and how they will react to sea rise, a specialist has observed and assessed them. This information will now be used to prioritise works and where to target further investigations.

The asset inspection looked for signs of deterioration, assigning a grading from 1 (very good) to 5 (very poor/failed). The grading estimates the assets remaining ‘useful’ life. For example,  how long until refurbishment and/or replacement of the asset is required. As part of this assessment, climate change projections such as sea level rise and increased storminess and rainfall totals are all considered. The information will help target further investigations and inform the sequence in which works are undertaken.  

Topographic Survey of the land and coastal defences between Steephill Cove and Monks Bay

Topographic Survey of the land and coastal defences between Steephill Cove and Monks Bay.

A topographic survey is an accurate depiction of a site that shows the natural and man-made features and their levels. It is done by land surveyors using specialised equipment and skills. 

The aim of the topographic survey is to gain a better insight into how the landscape will interact with any investigative works and identify problems before works commence.

Property Level Threshold Survey

In addition to the topography survey, property level threshold surveys have been completed. This is a process that assesses the level of flood risk to a property or site based on the critical water level entry points of the property. It is required for some developments located within flood zones.

The pictures below show Property Level Thresholds being assessed in Ventnor