Heavy rain predicted to cause more landslides

Climate change does not only alter the weather and has other impacts such as helping to trigger landslides.

Ireland can expect more landslides because of this, with major events arising every five years, according to an expert at NUI Galway.

The increasing frequency of significant landslides in Britain came up at the Festival of Science in Newcastle, with the view from the British Geological Survey unequivocal – more landslides are being triggered by our changing climate, with heavy rainfall the main cause.

The slides can occur when ground on a slope saturated with rain cannot support the extra weight. The soil and rock eventually gives way to come tumbling down the slope.

The last 14 months had seen a five-fold increase in the number of landslides recorded across Britain, said Dr Helen Reeves, of the British Geological Survey.

She said last year 176 landslides occurred in the five months to May. They might expect to see 50 in an entire year .

That year was the second wettest on the UK record books, and the survey sees a clear correlation between rainfall amounts and landslides.

Dr Reeves said 60 per cent of the events last year were directly caused by torrential rain.

Climate models
She said all climate models predicted that these heavy rain storms would increase in coming years to trigger more landslides that damaged communications and transport infrastructure.

The picture was no different in Ireland, said Dr Kieran Hickey, an expert in climate change at NUI Galway's school of geology and archaeology. The risk of landslides rose sharply in the 48 hours after heavy rainfall, the very events predicted to become more common.

He said in Ireland most slides involved saturated peat breaking away, and some of these were triggered by building work.

While we could get these “bog bursts” we have seen few damaging landslides in Ireland in recent years, said Dr Tiernan Henry, a hydrogeology expert at Galway’s school of natural sciences.

The two major ones were in 2003 in north Mayo and in Derrybrien, Co Galway. He said in Mayo it happened after a “100-year rainfall event” which followed an extended dry period. The peat had cracked and the water flowed directly to the peat-rock interface, and so moved the peat.