The Cliff Walk from Bray to Greystones has been closed since late February due to the cliff collapsing, at the Greystones end, following heavy rains. This erosion has been going on for ever though increased rain intensity from Global Warming has made it worse.
The Council engineer has proposed a short term solution of moving the walk back from the Cliff edge to by pass the worst area. This involves negotiating with landowners and should start immediately. I am urging this to happen as soon as possible as the walk is very busy.
In the longer term the surface water flowing over the edge will have to be reduced by piping and possibly by using the field for growing trees instead of crops, trees absorbing more water. This would also assist Biodiversity, soil stabilisation and amenity value. The recent Arup report on erosion on the railway from Dublin to Wicklow recommended a Detached Breakwater and an assessment of slope stabilisation techniques here.
I noticed 20 years ago that in heavy rain the cliff soil on the South side of Bray Head seems to become jelly like and it collapses and is washed away by the sea. I am glad that someone is finally prepared to consider how to slow erosion down.
Report on cliff collapse along Bray to Greystones Cliff Walk.March 2021 Initial Incident and Investigation
On the weekend of the 27th/28th of February, 2021, a collapse of the cliff along the Bray to Greystones Cliff Walk was reported. Wicklow County Council, An Garda Síochána and the Coastguard all inspected the area. It was found that 2 collapses had occurred within 40m of each other. The general area of the two collapses is shown on the imagery in Appendix A.
The photos taken at the scene at the time of inspection can be seen in Appendix B. As can be seen from these photos the collapses are immediately adjacent to the walk making the walk itself hazardous. The collapses extend all the way down to the beach, circa 20 metres or 65 feet below.Immediate Actions
It was decided at that time to fence off the affected location and to advise the public that the walk was closed as it was hazardous. It is simply not feasible to physically close off the Cliff Walk to the public. This was tried last year during the very first level 5 Covid-19 restrictions. Fences and barriers erected were simply pulled apart and broken, including private farmland fences and gates. Even when signs are erected and media campaigns advertising its closure and that it is hazardous the public do still walk it. See photos of immediate remedial actions in Appendix C.
Future ActionsShort Term
In the short term negotiations should start immediately with adjacent landowners to provide a temporary walkway away from the cliff edge to bypass the affected area. A possible route for theis temporary walkway is shown in Appendix D. The current cliff edge is unstable, cannot be deemed safe by any geotechnical experts and works to stabilise the cliff face are simply not a feasible solution as:
- The cost of any works would be prohibitively exorbitant.
- The works area is excessively hazardous and inaccessible due to
- Risk of further collapse from above
- High tide encroaches onto the base of the cliff face.
- Depending on the alignment of tides and the working day there would be very short working windows. No plant, machinery or materials could be left on the beach due to high tide and access to the base of the collapse could take 90 minutes from the Greytsones harbour Marina.
- Any works may only last a short while as a storm could undo the works.
Whilst the cliff is eroded partially be the sea, the main cause of the cliff erosion is surface water runoff from above. The cliff face has numerous surface water drainage outlets along its face just below the level of the cliff walk. These drainage outlets are taking surface and ground water away from all the farm fields between the cliff and the R761 Bray to Greystones regional road. Some of these drainage pipes date from when the railway line was first constructed. It is these concentrations of water at single locations that cause localised expedited erosion and ultimately collapses of the Cliff face. Such collapses will continue at an increasing rate due to climate change.
In order to protect the long term viability of the Cliff Walk, the walk itself must be moved inland and the rate of erosion from surface water runoff must be slowed down. There are a number of ways in which the surface water runoff can be dealt with.
- The existing pipes could be intercepted by a collector pipe running parallel to the cliff face and drained to a two locations where there are already stream outfalls to the sea. This option would have some negative aspects in that some of the existing pipe are over 2m below the cliff walk itself and so intercepting them and connecting them up would be challenging and costly. This option would also further increase the rate of erosion at the stream outlet points.
- The existing pipes could be removed. Allow for natural drainage ditches and ground infiltrations so that no build up concentrations of surface water runoff can develop but that natural percolation of the water through the ground occurs throughout.
- Accompanying either option A and B would be to slow down runoff rates from the land and increase surface water use on the land. This can be done by changing the lands from arable farming to natural woodland. The trees would use ever increasing amount of surface water as they grew. Further benefits of creating a woodland on Bray Head would be:
- Increase carbon sink value.
- Increase in local biodiversity
- Improve soil stabilisation
- Increased amenity value of the area between two of County Wicklow main towns.
It is a fact that the cliff will continue to erode and collapse as it has done possibly for the last 10,000 years, since the end of the last ice age. Therefore if we wish to protect this amenity for future generations we need to future proof it as best we can with current best practice. It is the opinion of the Councils Engineering, Climate Action and Heritage staff that a combination of options B and C are the most advantageous and sustainable for the future. Option A is heavy in engineering and would create a future issue that would also be costly and require a solution heavy in engineering to solve.
Appendix A – Location of Collapses
Appendix B – Incident Inspection Photos
Appendix C – Remedial Actions
Appendix D – Temporary Bypass Route
Click Here For information. Erosion Arup2 – 21.