Rail passengers travelling with Iarnród Èireann-Irish Rail from Dublin to Wicklow can enjoy spectacular views of the sea and coast from an escarpment that in some places drops 25 metres down to the sea.
Part of the Irish Rail’s eastern line runs along the coast and until the year 2000, erosion steadily undermined the old and unstable coastal defence and the tracks, as huge waves crashed onto the shore when high tides coincided with stormy weather.
As a consequence, the 150-year-old railway took a battering. Lack of public funds prevented the necessary maintenance work from being done until quite recently.
COWI began working with Irish Rail in 2000, helping to develop their coastal defence programme, particularly long the sections where there was an increased risk of accidents due to erosion. The programme continues to this day.
Rock steady
The coastal defence programme primarily involves rubble mound revetments. These are strategically placed along the coast between the beach and the railway at the most exposed locations.
Revetments have proven to be the best and most cost-effective solution, both along the sandy beaches and in front of the headland embankments where the railway is built high above the sea.
"The railway couldn’t be moved inland, so to make it safe it had to be fortified along the eroding cliffs. However, the most vulnerable sections of beach will gradually disappear in front of the revetments. Near cities there is little space for realigning the infrastructure, and in order to minimise maintenance, a substantial and permanent solution such as rubble mound revetments is required to prevent the sea from damaging the railway," says Christian Helledie, a coastal morphologist at COWI.
The Irish Sea is known for its harsh impact on the coastline. Because of the hostile wave climate and deep water along the shore, beach nourishment programmes along the coast are both too expensive and demanding. Also, local environmental agencies resist granting approval of such projects because of the extensive volume of sand materials required.
By Gitte Roe Eriksen, cht@cowi.comPublished: 12.08.2008