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Landslides were a ‘one-in-3,000-year’ event

Floods wreaked havoc last August.

EXPERTS have reassured farmers in Glenelly that devastating landslides last August were a ‘one-in -3,000-year event’.

Addressing a packed-out Cranagh Hall, Dr Alan Dykes from Kingston University claimed the chances of another bout of landslides, which resulted from a freak 50mm rainfall in three hours, is “vanishingly small”.

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The public meeting hosted by DAERA provided an in-depth look at the cause of the destruction to some 40 farmer’s land from the local area.

“This is such a rare event, it is astonishing,” Dr Dykes said. “50mm of rainfall within three hours is a once-in-3000-year event. With no radar data obtained for August 22, I estimate this amount was much higher in the Glenelly Valley.” 

Overall, the rainfall caused a total of 13 ‘slide zones’, each comprising of several individual landslides. Having spent two days studying the aftermath of August’s landslides, Dykes explained they occurred when peat soils in Glenelly became saturated and water could not pass through an impermeable ‘iron pan’ mineral layer. As pressure increased, the saturated soils moved down the valley.

“The peat that slid down the mountain formed 10,000 years ago – that’s how rare it is. The Glenelly Valley is unlikely to see more landslides because of the way the hillside responds.”

With the prospect of future landslides incredibly small, farmers were advised that the best thing to do with the landslides was to leave them alone.

“Nothing will be gained from trying to modify the landscape and there may be adverse effects,” Dykes said. “It would be a waste of time, money and resources. 

“As well as this, afforestation may reduce the likelihood of future landscapes from vanishingly small to even more vanishingly small.”

Dykes assured farmers that the effected landslides would dry out and revegetate over time, with considerable effects being seen over a five year period.

Independent councillor Patsy Kelly felt it was important planners and councillors had access to Dyke’s findings.

“I feel this information must be passed on to council,” Cllr Kelly said. 

“I feel it would be relevant to planners and especially those involved in wind farms around the area. The threat of landslides poses a problem to wind farms and it is something developers need to take into account, even if chances of a landslide are vanishingly small.

“Overall, I was pleased to see a technical element to the meetings.”
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