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een very important in populating the database fields for the events. The initial search of reference sources hasidentified 117 events. Many more events will be identified in future research, as has been found in the Breifneproject. The preliminary analysis indicated that Co. Wicklow has the most events (14), followed by Co. Mayo(12), and Co. Antrim (10). The majority of events (63) involved peat as the main material, while some 31 werecomposed of coarse debris.At Pollatomish in northwest Mayo over 40 catastrophic landslides occurred on the night of Friday 19 th September2003. This was due to exceptionally heavy rainfall in the area. Extensive damage was done to roads, bridges,and houses. The majority of failures involved the sliding and flowing of peat down the hillside. It was concludedthat, due to the contraction of the peat after a very dry summer, the excessive rainwater could gain rapidaccess saturating the peat mass very quickly and making it buoyant. This process was aided by the presenceof an impermeable hard pan at the peat-mineral soil interface.The Derrybrien landslide occurred on 16 th October 2003. It was located on a wind farm construction site on theSlieve Aughty Hills just to the north of Derrybrien village. The site is covered with blanket bog. From the failuresite the peat flowed down into a local stream and then into the main river which eventually reached LoughCutra, causing a major fish kill there. It was concluded that there were two contributory factors, a zone of weakpeat and proximity of a natural drainage channel. Activity associated with the wind farm construction was alsofelt to be a contributory factor.4. Geotechnics of LandslidesGeotechnics of landslides is concerned with the failure mechanisms of soil and rock through an analysis oftheir strength parameters and the effect of water on those parameters. The geotechnical factors are separatedinto those relating to “mineral” soils, those relating to organic soils such as peat, and those relating to rock.Strength at failure is expressed in terms of the shear strength parameters, cohesion and angle of shearingresistance. Many landslides occur during or after heavy rain. Water has two main detrimental effects – itreduces the force resisting instability and increases those causing the instability. Water can also destabiliseslopes where water seeps from an exposed face, as is the case where there is a sand layer in an exposed faceof glacial till.In Ireland “Mineral” soils are predominately glacially-derived. Glacial tills (or boulder clays) have high angles ofshearing resistance, typically 30º to 35º. Very steep slopes can be cut in these soils in the short term but theywill eventually fail due to the dissipation of soil suction forces. They are also subject to internal erosion. Pureclay soils are rarely encountered in Ireland.Landslides involving peat, in both raised and blanket bog, make up a significant number of events in the IrishLandslides Database. Blanket bog failures are more common in the wetter autumn and winter periods, whilethose in raised bogs can occur at any time in the year. Water can make up to 90% of the peat mass, thustending it to flow when it fails. Excess water pressure at the base can result in uplift and then downslope failurecan occur. Man’s activities such as turf cutting or land drainage can also cause failure. There is a strongcorrelation between high rainfall and peat slides, as occurred at Pollatomish. The fibre structure of peat is alsoimportant. Increased humification with depth can produce weak layers which can be the source of failure.Landslides in rock are common in upland areas where steep rock faces occur. They can take the form of freefalls through air, topples about a pivot point, or slides which may be rotational or translational in form. They canoccur because of the weakening of the rock by chemical weathering, physical weathering due to frost shattering,or movement along discontinuities in the rock such as bedding planes, joints or faults.The geotechnical properties of Irish earth materials, particularly peat, need to be investigated with specialreference to slope instability. Fundamental research is needed on the behaviour of peat at low effective stresses,and methods are needed to more accurately measure the strength properties of peat which are relevant to peatslides. Mineral soils prone to landslides also need to be identified.5. Landslide Susceptibility Mapping in IrelandEven though Ireland is not a high-risk zone for major landslides, landslides do occur and it is thus important toundertake landslide hazard and risk assessment. Such assessments are the subject of much researchinternationally with regard to the methodologies used. The terminology can be confusing as risk, hazard,vulnerability, and susceptibility are defined differently by different workers. The terminology of the United Statesiii