Review of the 2007 Dunwich coastal defence project
An assessment of the results of a project to stabilise the beach in front of the cliffs protecting Dunwich village on the Suffolk coast.
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Details
Background
In March 2007, work was completed to trial a new, low cost technique to stabilise the beach in front of the cliffs protecting Dunwich village on the Suffolk coast. Eight ‘geo-humps’ were constructed along the beach made of geomembrane structures filled with beach shingle and sand from the local area.
Following this, monitoring was undertaken for five years to investigate the hydraulic performance and the condition of the various elements. The monitoring regime consisted of a series of:
- beach cross-sections
- aerial photographs
- visual inspections
Outcome
The results of this demonstration project have provided the Environment Agency, local authorities and coastal defence practitioners with valuable and real-life information about the application of this new low cost technique for beach stabilisation. If the approach proves effective in the long-term, it may have potential for replication elsewhere in the UK.
The project showed that the use of geomembranes and local beach material can provide a low-cost option for constructing structures to stabilise eroding beaches.
The monitoring data indicates that the structures may have been in place during a period of relative calm, when the beach has been building up naturally. As the humps have not yet experienced long periods of pressure from the weather and sea conditions, the project team recommended that they remain in place. This was to allow for continued monitoring. Decisions about the long-term impacts and effectiveness can then be made.
There was no evidence that the structures were having a major impact on the condition of the sites of special scientific interest (SSSI) or interrupting shoreline processes.
The equipment used to construct schemes of this type must be carefully selected. Further work must be done to determine how best to position the geotextile without affecting the design shape of the ‘geo-humps’.
This research project began in 2006 and was completed in 2013.