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The floods that inundated Clifden in Co Galway within hours is a clear sign that Ireland’s weather extremes will continue to worsen, warned one of the country’s leading climate change experts.
Professor Peter Thorne said that a “very large” number of cities and towns across the country are equally susceptible to “truly catastrophic” flash floods due to their catchment around a river.
Dismissing speculation that drainage at Sitka spruce plantations outside of Clifden were to blame for Wednesday morning’s flooding, Professor Thorne said it was due to the “end of Hurricane Laura” crashing into the surrounding mountains. from the seaside town of Conneamara.
“When you’ve got all that deep, humid tropical atmosphere, traveling across a silky smooth Atlantic, the first thing it does is hit the mountains and hills of Clifden, and it’s like squeezing a sponge,” he said.
The Maynooth University academic, who was the lead author of the fifth assessment report of the UN Intergovernmental Panel on Climate Change, said the soil was also “unusually saturated” as each of the past three months was more humid than normal.
Small rivers like the Owenglin in Clifden are also “very sensitive to heavy rain,” he said.
Noting the devastating impact of small rivers flooding parts of Inishowen, Co Donegal in August 2017, Professor Thorne said that many towns and villages face a similar fate, historically occurring every few years.
“The climate is one degree warmer than it was in the 19th century due to man-made emissions, and for every degree of temperature rise, the atmosphere contains seven percent more water,” he said.
“Basically, what goes up must come down. With more water in the atmosphere, when it rains, it rains with greater intensity ”.
Climate model projections “strongly” suggest that the trend will continue.
“It is getting worse and it will continue to get worse until we can stabilize global temperature changes,” he added.
“There is no good science on whether the frequency (of flood events) will increase, but the intensity of the events will be worse, it is a case of getting used to the idea that our extremes will be more extreme.
“Something that was once considered a one-time event in a century nationally could become an event of one in 20 years.”
At the time of the Clifden flood, there was only a yellow rain warning for Donegal, Leitrim, Mayo and Sligo counties.
Evelyn Cusack, chief forecasting officer at Met Éireann, said it was a “forecast error” that was partly due to their modeling systems, which “have a bit of difficulty” predicting rainfall from a tropical air mass, which they are unusual in Ireland.
“It was a forecast flaw in terms of the amount of rain, but Met Eireann would not be predicting flooding or river flow,” he said. “We would not be predicting the impact.” Met Eireann had forecast 20mm of rain in the area, when around 60mm fell overnight.
Following the storm surge in Clifden, which forced the evacuation of homes and two schools, claims emerged on social media that drainage in large swamps of swamp outside the city that have been turned into Sitka spruce plantations, managed by Coillte, helped speed up the process. flood.
But Dr. Tiernan Henry, a geoscientist and surface water expert at NUI Galway, said he would be “very reluctant to point the finger at forestry.”
Records at the nearby Mace Head weather station showed 27 ml of rain falling in three to four hours, he said. “That’s essentially a quarter of the September average monthly precipitation in that area that occurs in just a few hours,” he added.
“It was a very heavy rain event.” Dr. Henry said the “most important factor” was the “unusual amount of rain” falling in a relatively steep catchment over a “striking river.”
Coillte also questioned the speculation. Pat Neville, communications manager for the semi-state forestry company, said it operates two plantations near Clifden, which were identified on social media as culprits.
Water drains from the larger of the two remote Clifden plantations, he said, adding that the drains in the forests are shallow and have long been “clogged” with debris as they were planted more than 40 years ago and they are not maintained.
“We had an extraordinary amount of rain in a short time. To point the finger at the planting, to say that that was the cause of the flood in Clifden, it would be quite unfair, ”he said.
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