Landslide risk puts us in danger zone

Donal Hickey on a threat we need to take seriously.

PEOPLE living in towns such as Mallow, Fermoy, and Newcastle West are well aware of problems caused by flooding, but heavy rain can also cause landslides.

A new report says the risk of landslides in Ireland is greater than was previously thought. The report, by a team from universities and state agencies, says climate change, growing urbanisation, and increased infrastructure projects are the root of the problem.

Landslides result in substantial property damage and loss of life every year, worldwide. They can be triggered by earthquakes, volcanic eruptions, heavy rainfall, or human activity. Ireland is not high risk for major landslides compared to other countries. The historic record includes a few serious events, such as that at Castlegarde, in Co Limerick, when 21 people died.

In 2003, landslides at Pollathomas, Co Mayo, and Derrybrien, Co Galway, highlighted this issue and it became clear there was no collated information, either on the historic record or on the risk of landslides in the future. The Geological Society of Ireland (GSI), in response to the 2003 events, visited Co Mayo, compiled a brief report on what happened and began a wider study of landslides in Ireland.

Landslides are a hazard to life and property, and, while no one has been killed recently, 34 people have lost their lives in such events in Ireland. The most common feature of landslides is that they follow periods of heavy rain that destabilise the surface and ‘lubricate’ earth movements

The communities in Derrybrien and Pollathomas were stunned by the destructive power of the landslides, which resulted in millions of euro worth of damage. At Pollathomas, where 40 houses were evacuated, damage was estimated at €10m.

Last month, the European Court of Justice ruled against Ireland in a case involving a wind farm project at Derrybrien, where a landslide killed tens of thousands of fish. The court said a proper environmental impact assessment should have been carried out before the project proceeded. The Derrybrien wind farm project was the biggest in Ireland, at the time, and one of the largest in Europe.

The ruling will have major implications for the way the Government allows other projects to proceed before full environmental checks, required under EU law, have been carried out.

At Derrybrien, 450,000 cubic metres of peat were dislodged over a 32km area, polluting a river and killing 50,000 fish. The Government argued that this was caused by poor construction work, but the court found that it was because a proper environmental impact assessment (EIA) had not been carried out.

The ruling covers other cases in which an EIA was done only after work had begun. These include quarry developments in counties Offaly, Galway, Waterford, Clare and Monaghan; pig-rearing, peat-extraction and wood-processing enterprises in other counties; a hotel in Co Kildare that received retention permission only after it was built; and a convention centre in Co Dublin where work began without proper planning approval. The court ruled that retention permission could be applied only in exceptional circumstances and argued, in effect, that Irish law was too loose.

In its latest report, the Geological Survey Office warns of an ongoing and underestimated risk of serious landslides in potentially hazardous areas. It says surveys of these areas should be undertaken and the Government should introduce more stringent planning controls to curb the risk, and the cost, of future landslides.

The expert group says steps need to be taken to integrate landslide issues into the planning process. It further warns there will be increased landslide activity as development in Ireland increases, and expands, in the years ahead.

The Geological Survey of Ireland (GSI) has awarded a contract to consultants, Mouchel Ireland Ltd, to undertake landslide susceptibility mapping in two designated areas in Leinster and Munster. The contract began in June and will continue for several years.

In Leinster, the area stretches from Clogher Head, in Co Louth, down to Arklow and west, as far as Trim and Newbridge. In Munster, the area extends from the hills north of Cork city to the sea, and from Bandon eastwards to Killeagh. The study in both areas will include the coastal zones.

These two areas include the country’s major development zones, in terms of infrastructure, housing and commercial development. “The project is important, in the context of climate change, where more intense rainfall is predicted for Ireland, as well as higher sea levels affecting the coastal zone,” says the GSI.

An in-depth analysis of the landscape should identify areas prone to landsliding, and should also provide important information to planning authorities in relation to development control.

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