Landslides Workshop
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GSI Landslides Workshop
– 21 April 2009

Ronnie Creighton

The GSI ran a major Landslides Workshop in our offices on 21 April 2009. This was the first workshop of its kind in Ireland with an attendance of 90. The two main aims of the workshop were to introduce the GSI landslides susceptibility mapping project and also to provide a forum for presentations on current landslide research in Ireland. The large attendance reflects the importance of landslide hazards in Ireland today, and indeed the serious impacts that landslides can have.

Landslide event in Pollatomish
Figure 1: The landslide event in Pollatomish, September 2003

The background to this workshop goes back several years. Subsequent to the Pollatomish (Figure 1) and Derrybrien landslides in the autumn of 2003 the GSI established a Landslides Working Group to examine the whole area of landslides in Ireland for the first time. The report of the Working Group, "Landslides in Ireland", was published in August 2006. The report made several major recommendations for future work. These included the continued development of a national database of past landslide events; the promotion of geotechnical research into the principal landslide materials such as peat; landslide susceptibility mapping across the country on a phased basis; the inclusion of landslide data in the planning process; and increasing public awareness of landslide hazard. An important point to emerge from this report was the multi-disciplinary nature of landslides research.

This range of expertise was reflected in the wide range of stakeholders who attended the workshop. They included geologists, geomorphologists, geotechnical engineers, planners, GIS specialists, ecologists, botanists, and other environmental scientists. Attendees represented a wide range of institutions including government departments, state and semi-state agencies, local authorities, universities, consulting engineering firms and wind farm developers. This mix of expertise resulted in lively debate on the presentations throughout the day.

Ronnie Creighton, GSI, who co-ordinated the workshop had allocated the presentations into three broad groups - landslide susceptibility mapping methodologies and GIS technologies; geotechnical engineering research; and landslides within the planning process. The keynote presentation was on the GSI landslide susceptibility mapping project which commenced in June 2008. This was given by Robert Bone and Stefan Morrocco of Mouchel Ireland Ltd. who are the consultants working on the project. The consultants’ brief is to build a landslides inventory of past events and produce landslide susceptibility maps for two designated areas of Ireland, namely East Leinster and the Greater Cork City Area (Figure 2). The intention is that these maps will be robust enough to introduce into the planning sphere both in development plans and in development control. The Department of Environment, Heritage, and Local Government (DEHLG) is very supportive of this project. The Mouchel consultants described the datasets they were using and also their proposed susceptibility mapping methodology.


(a)
Greater Cork area
Figure 2: Proposed landslide susceptibility mapping areas (a) Greater Cork City area
and (b) The East Leinster area

(b)
East Leinster area
Basemap images from NASA/JPL/NGA

Tim McCarthy from the National Centre for Geocomputation (NCG) at Maynooth (NUIM) then described some recent developments in geotechnologies for landslide mapping and monitoring. There were clearly new technologies coming on stream which would be very useful for landslide mapping and monitoring in the future. Alexei Pozdnoukhov (NCG) and Xavi Pellicer (GSI) then discussed their ongoing remodelling of the Breifne area landslide data from the Landslides in Ireland report. This new work will substantially improve the modelling of the landslide susceptibility for the Breifne area. The final presentation on mapping methods was given by David Fleming of the RPS Group, who talked about the mapping of peat instability in Ireland (Figure 3).

Peat stability assessment map
Figure 3: Peat stability assessment map

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Two geotechnical presentations were given on the strength of peat and glacial till in the context of slope stability by Mike Long and Ken Gavin, UCD. Their talks emphasised the complexity of measuring the strength of these materials. Jim Casey from the OPW described Ireland’s coastal protection strategy. He outlined the various high resolution coastal surveys that had been completed and the assessment of erosion rates and flooding susceptibility. This work is linked to the European EUROSION project.

There were two contrasting presentations from Northern Ireland. Terry Johnston (GSNI) gave an overview of landslide hazards in Northern Ireland, showing examples from the basalt escarpments on the east and north coasts (Figure 4). They have had a significant impact on infrastructure. In contrast, Mark Cassidy of Byrne Looby Partners gave a practical example of a road repair after a landslide. The road in question was the Torr Head Coast Road in Co. Antrim. He described the geotechnical assessment and the remediation work done to repair the road.

Derry - Belfast train following a rockfall
Figure 4: The Derry – Belfast train following the Downhill Rockfall, June 2002


The final session of the day covered planning issues. Aileen Doyle from DEHLG gave a general overview of the planning system in Ireland and emphasised the standards that would have to be met if landslide data was to be incorporated into the planning process, either in development plans or in development control. She was very supportive of the GSI project but was keen that everyone should be aware of the downstream ramifications of the inclusion of landslide susceptibility maps in the planning process. The day finished with two practical planning examples. Eamonn Hore from Wexford described the coastal erosion problems in Wexford from a planning perspective and the great danger to settlements close to the shore (Figure 5). Ian Douglas from Mayo described the planning difficulties encountered in the area subsequent to the Pollatomish landslides of 2003.

White Cliffs of Blackwater
Figure 5: The White Cliffs of Blackwater

The repair and mitigation measures were very expensive. He emphasised the need for susceptibility mapping to be undertaken as soon as possible.

The workshop ended with a short concluding discussion. The diverse nature of landslide issues was emphasised as was the need for more inter-disciplinary work. The importance of landslide susceptibility mapping was also stressed. The papers throughout the day had also repeatedly referred to the impacts of climate change where Ireland is expected to experience more intensive rainfall events in the winter months and in northwest Ireland where there are many vulnerable slopes. The attendees praised the high quality of the presentations throughout the day. It was hoped to repeat the workshop in 2010 when an update on landslide research could be given.

For further information and to see the presentations please visit www.gsi.ie/Programmes/Quaternary+Geotechnical/Landslides/Landslides+Workshop+2009.htm


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