Part of Dublin's Great South Wall will be closed to the public for a number of weeks from today while Dublin Port carries out urgent remedial work following damage caused by Storm Bram.
The authority says the sea wall, which plays a key role in keeping ships safe as they enter the port, is coming under increasing pressure from severe weather events.
Built between 1720 and 1795, the wall, forming part of the Poolbeg Peninsula, was constructed to shelter the shipping channel.
231 years later, it remains a key piece of marine infrastructure, safeguarding the passage of €165bn worth of goods that come and go from the port every year.
However, the structure is under pressure from severe weather and last December it took a battering from Storm Bram, which hit Ireland on 8 December last year, requiring repairs that will cost €2.5m.
Port Engineer Eamon McElroy said the storm, which was the fifth most severe recorded in the Irish Sea, shifted rocks weighing between two and four tonnes from around the base of the wall, displacing some and washing others completely away.
"The damage was caused to the rock armour that protects the Great South Wall and Poolbeg Lighthouse," he said.
"Storm Bram moved so much rock within that one 12-hour window, compared to the previous ten years combined.
"That made us want to react very quickly so that we have enough resilience in the rock armour because nobody knows when the next Beast from the East is coming.
"We're going to bring local stone, which we've sourced in Arklow and is of the correct grade and correct strength, and we're going to plug up all the gaps."
But Mr McElroy said that in the longer term, the port will apply for planning permission to upgrade all of the rocks around the wall because of the pressure it is under from severe weather
"We're going to bring in 15 tonnes of rocks from Norway and we'll build up the revetment again all around the Poolbeg Lighthouse and all the way down to the Half Moon Swimming Club," he said.
"That will give us more resilience to deal with these more severe storms that we're beginning to experience more frequently."
"The Great South Wall and Poolbeg are over 200 years old and they're actually built on sand, they don't have any foundations.
"In 1995, we introduced the rock armour to give it protection, so it was designed for the storms of the mid-90s but the storms we are getting now, we are finding the wave energy is far higher than what we experienced back then.
"We actually monitor the rocks. We use laser scanning for the deck and the Poolbeg Lighthouse and other technology and we are able to build a 3D model.
"We started that back in 2015. Every year we repeat that 3D model and we overlap them on top of each other and that can tell us what rock armour has moved."
The urgent remedial works require the partial closure of the 5km wall for the next five weeks.
Dublin Port Head of External Affairs Claire Percy said the wall is also an important recreational amenity for the capital but appealed to those who use it to comply with the temporary restrictions.
"We can have 100,000 people walking the wall each year. These works are really important to protect the amenity right now and into the future," she said.
"The last 100 metres or so will be closed around the Poolbeg Lighthouse and we ask people to respect that cordon."
The Great South Wall works in tandem with the North Bull Wall to prevent the silting up of the mouth of the Liffey and providing a safe harbour for shipping.
Both walls are breakwaters and create an increased tidal flow out of the Liffey, which keeps sediment and silt from building up, making it easier to maintain the required depths for shipping.
The wall is fully closed to the public during severe weather events.
That happened just once in 2023, but rose to four times in 2025, and this year it has already been closed on a number of occasions, showing the pressure that storms are placing on the structure.
