Coastal Squeeze and Rollback

It is generally accepted that sea-levels are rising in Britain, although there are many opinions about the causes and the rates. Most scientists believe that the rate of sea-level rise has already accelerated and will continue to do so until levels of atmospheric carbon-dioxide start to be reduced.

Regardless of the cause or rate of sea-level rise the effects are the same, in a natural system land is “lost” and becomes sea. With a high coastline this manifests itself as erosion of the cliffs, but with a gently rising coastline the result is a slow movement of the shoreline inland – so over time a particular piece of land will change from dry land to shoreline shingle or mud, then foreshore and eventually to sea. The rate of change will depend on sea-level rise, but also on how “dynamic” the environment – how exposed it is to tide and waves.

In the case of a defended coastline if defences are maintained and increased to take into account the sea-level rise (Hold the Line in SMP’s etc) this results in the seaward side of the defence continuing to develop naturally – ie change from foreshore to sea, but the landward side remains the same. The result, known as “Coastal Squeeze” is that the foreshore (Sand, shingle or salt-marsh) is slowly lost together with the natural transition zone from land to sea.

The habitats of these ephemeral transition zones are both rare and important and as a result many are designated under international, European and National designations which require them to be protected.

We are very fortunate locally as the New Forest Coastline contains some of few areas where there is natural gently rising coastline. This is rare, particularly in Southern England, where most of coastline is heavily managed and defended to provide flood and erosion protection. These areas show a natural graduation from farmland, often to a narrow strip of woodland, then to a foreshore, often with the remains of fallen trees, to foreshore and salt-marsh.

The narrow strip of woodland provides a unique habitat, and the tree-roots will slow, and control the rate erosion. The fallen trees also provide a unique habitat and make the shoreline interesting and very different from most other places.

Within the Solent Protection Society we believe that these unique habitats should be maintained, by natural processes, and that they cannot be maintained by traditional engineering works. The most effective way to maintain the habitat is to allow natural roll-back. This should be done by allowing natural regeneration of indigenous vegetation, particularly woodland, along a margin between farmland and the coastal strip.

We would welcome members opinion of how these habitats should be managed and whether this should be funded by public authorities, or whether the landowner should be expected to manage appropriately.

Innovative sea defence repairs using ‘Concrete Canvas’

We are interested to note this piece from the Eastern Solent Coastal Partnership website.  Parts of the sea defences on the Warblington shore line, compromised during last winter’s storms, have been effectively repaired using a new technique.  IMG_5065

The repairs commenced on 1st August 2018 to the worst damaged sections of wall, where the concrete rendering had detached itself from the main wall structure and was laying on the foreshore of the harbour. The works were delivered by ESCP and were carried out by contractors Graham Attrill Civil Engineering Ltd., from the Isle of Wight on behalf of Havant Borough Council.

Within two weeks the works were completed using an innovative material called Concrete Canvas, used by Havant Borough Council for the first time. The Concrete Canvas was delivered to site as a roll of concrete impregnated fabric, which was cut to length and draped oIMG_5116ver the wall, allowing the fabric to follow the contours of the internal wall beneath. Once in place, the fabric was sprayed with freshwater to activate a concrete fibre embedded within.  The concrete fibre forms an impermeable, energy absorbing concrete casing, perfect for withstanding wave action. The material repaired the seawall and will protect the internal structure from further erosion.

Following completion of the works, ESCP staff will continue to monitor coastal structures within the harbour on an annual basis. This will help inform any future works and allow ESCP to identify changes in structure condition within the HBC borough.

(Information Source – Eastern Solent Coastal Partnership.)

Southsea Seafront consultation closes on the 27 August

The Southsea Coastal Scheme have had well over a thousand survey responses so far – but still want more.

You can view the consultation materials here. There is scheme visualisation on YouTube here with audio description. If you visited their events and want to jump straight to the survey, you can find it here.

Once the feedback has been analysed, a cross-party working group at Portsmouth City Council will review the evidence and make a decision on which options to take forward. The Southsea Coastal Scheme will hold further public exhibitions in early November, before seeking planning permission towards the end of this year. Residents will again be able to give feedback to the council at this stage.

The consultation closes at 11.59pm on Monday 27 August 2018.