Ireland has no national "hazard" map for planning authorities which could warn of events such as the recent landslides in Mayo and south Galway, according to the Geological Survey of Ireland (GSI).
The GSI is convening a national landslide working group today to examine compilation of a database of events and an associated "hazard" map. It also aims to produce advisory booklets for local authorities which would highlight the need to ensure that there is a geological input to scrutiny of planning submissions and associated environmental impact statements.
Over 50 events recorded by geologists to date - including over 40 "bog bursts" in the last century alone - would be used as a foundation for the database. These include a previous "failure" in the Slieve Aughty area of south Galway - the region where the Derrybrien landslide occurred last October - and a major bogflow in south-west Donegal in 1945 which travelled over a kilometre and blocked a local road.
Consultants' reports on the Derrybrien landslide are still being finalised by Hibernian Wind Energy and by Galway County Council; while consultants for Mayo County Council have recommended a €5 million remedial plan for the Pollathomas area of north Mayo. In an observation compiled by GSI geologists on Derrybrien, it notes that the Derrybrien landslide was quite different to that of Pollathomas, which occurred last September and forced some 40 families out of their homes.
The Pollathomas landslide on a steep slope of thin peat cover, as well as subsoil and rock material, appeared to have been triggered by a very heavy rain storm, it notes. The Derrybrien failure occurred during dry weather - after a prolonged dry period in August. One common factor is that both events occurred in areas of poorly permeable bedrock, the GSI says.
