Canvey Island Sea Wall Erosion, should be the Real Focus of CPBC’s Attention. Residents again being kept in the Dark?

The condition of the Canvey Sea Wall, or Sea Defence system, is causing serious concern, despite the lack of news or information.

The cause, which should not be too surprising, is currently under investigation.

Further inland on Canvey a large Green Belt site, identified as being deliverable and developable by Castle Point borough council, was the subject of a pre-development Ground Investigation Report, probably the first, and most thorough investigations of its type on Canvey Island, to be made public via the cpbc planning portal.

The Ground Investigation Report indicated what should be serious concerns to the cpbc development committee and planning officers, should they refer to it and give it the respect it warrants.

We suspect, however, committee members are unaware of its existence!

Despite this site being a full Kilometre from the Estuary, the effects of tidal water which surrounds Canvey Island have been found!

The Ground Investigation Report was carried out to consider what Risk the subsoil and water table might have on development structures, such as Housing.

It found;

Geotechnical Risks*
Poor bearing capacities of the low strength / loose soils;
Aggressive ground and groundwater conditions
Shallow groundwater (possibly under tidal influence)

The High Water table found on Canvey Island is well known to residents, however what was surprising is that this water consisted of a level of saline, or sea water, content!

In effect our Sea Defence is incapable of stopping Tidal Water from penetrating UNDER the sea wall.

If these influences can be found 1 kilometre from the sea wall, how much more damaging are they to the Sea Defence itself?

The constant changes via the ground water saturation and drying processes, and the less than stable subsoil beneath the Sea Defence foundations will over time, challenge the longevity of the structure. Whilst the effects of the Tide itself is more obvious!

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The effects of the more frequent passing of larger and larger transport vessels along the Thames, requires monitoring, as does the constant dredging.

As recently as September 2017 we were reassured that these Sea Defences are “well maintained”, and whilst these images probably indicate superficial damage we have learnt that the Environment Agency have identified some areas of the Sea Defence causing them serious concerns!

The Environment Agency are known to have carried out surveying inspection works and are considering what steps are required to maintain the integrity of the Canvey Island Sea Defence.

*Geotechnical engineering is the branch of civil engineering concerned with the engineering behaviour of earth materials

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4 responses to “Canvey Island Sea Wall Erosion, should be the Real Focus of CPBC’s Attention. Residents again being kept in the Dark?

  1. Canvey Shoreline Investigation works.
    The Environment Agency in April of 2017 began ground investigation works along the southern shoreline and Canvey Island frontage. These works entailed extracting cylindrical lengths of soil to provide data so as to determine the full extent of the ground conditions that the seawall is sitting in. It will then be possible to confirm if any works are required to ensure that the fixed defence is able to continue providing flood defence to Canvey Island for many years to come.

    This work is part of the Thames Estuary Assessment Management 2100 programme (TEAM2100) delivering the first 10 years of Capital investment in the tidal flood defences of the Thames Estuary as recommended by the Thames Estuary 2100 Plan.

    We are now informed of the outcome of this investigation via a summary of a 600 page report, indicating that:-

    “The intrusive geotechnical testing results along the flood defences at Canvey Island show the embankment/ground is comprised of clays with some layers of silt and sand. The defenses to the west of Thorney Bay along the south end of Canvey Island are in good condition and are performing as expected. The defenses to the east of Thorney Bay along the south end of Canvey Island will be repaired/replaced in key locations to ensure the barrier continues to perform as expected. Several in-field tests were obtained including Standard Penetration Tests, Hand Vane and Pocket Penetrometer Tests, Headspace Screening of Environmental Samples, Variable Head Permeability Tests, and Dissipation Tests. In the laboratory the following tests were performed: Particle Size Analysis, Dispersion Tests, One Dimensional Consolidation Tests, Permeability Tests, Undrained Triaxial Compression Tests, Effective Stress Triaxial Compression Tests, Shear Box Tests, Unconfined Compressive Strength Tests in Soil, and Chemical Analysis. The information gathered will ensure the engineers have sufficient information on the ground conditions to design the correct repair/replacement method”

    It is hoped that the full report will be released in due course.

    Clearly the long term sustainability of Canvey Island and the safety of its community depends totally upon the availability of the funding costs needed for the maintenance and improvements of its sea defence. Canvey Island will need to compete for the funding, aimed at reducing the risk of tidal and fluvial flooding to 1.25million people and £200 billion worth of property as part of the aspirational Thames Estuary 2100 project.

    To give some idea of the magnitude of the task needed to be undertaken, this work covers the River Thames flood defences between Teddington in the west and Shoeburyness, and the Isle of Grain on the Kent coast.

    The Environment Agency when acting as Statutory Planning Consultees identify to CPBC that there are no guarantees that flood risk can be eliminated and that Government funding has yet to fully materialise.

    In most cases the risk may be acceptable however there is a clear understanding, as in the case of Canvey Island, that the flooding of a defended area could have catastrophic ramification.

  2. stirringsinthefanns

    Reblogged this on and commented:
    As we’ve stated before, we’re not NIMBYs and we have no problem with truly affordable homes being built – in a sustainable way – where they’re needed along with the infrastructure to support the expanded population. However, sometimes there are circumstances where there are sound, rational reasons why new housing shouldn’t be built in certain locations. Canvey Island, which is below sea level at high tide, is one of those locations, particularly when the inadequate transport infrastructure and the presence of petro-chemical facilities on the island is taken into account. None of this seems to be understood by Castle Point Council who in a bid to keep the mainland part of the borough as green and leafy as possible, are willing to overload a flood prone island with even more housing! Maybe, just maybe, the findings of a ground investigation might start to make the council reconsider their position…

  3. Which Green Belt site do you refer to and is the Ground Investigation Report available for the public?

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