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5.1.4 Mapping and GISBy definition, landslide hazard will be determined by where the potential for landslides occurs, and similarlyrisk will be estimated based on the location of people or assets in geographic proximity to such hazard. Thispoints to the extreme significance of mapping in any deployment and implementation of a landslide hazardmitigation strategy. Essentially, the successful management of landslide hazard will be predicated on knowingwhere such hazards are likely to occur. It is only within a spatial framework that landslide hazard can beoptimally understood and dealt with. Map products are therefore a very important part of landslide hazardmanagement, and the availability of map outputs are of huge benefit to government departments, state agencies,local authorities, engineers, and the public in general.GISThe development of Geographic Information System (GIS) technology has greatly facilitated spatial analysisand the creation of useful map outputs. Although the term GIS is often thought of as being a particular type ofsoftware, GIS is more correctly defined as a system of computer software, hardware and data, and personnel,to help manipulate, analyze and present information that is tied to a spatial location. GIS is a systematicmethod to visualize, manipulate, analyze, and display spatial data. Simply put, a GIS combines layers ofinformation about a place to give a better understanding of that place.VegetationGeologySoilsDrainageSusceptibilityAssessmentFig. 5.2 The concept of overlay analysis in GISFig. 5.2 is a simple graphic representation of how spatial data layers can be combined in an overlay analysisthus yielding new information about a location. In this figure data layers such as vegetation, geology, soils anddrainage networks are shown in overlay fashion, correctly located with respect to each other. These layers canbe analysed in association with the occurrence of landslide events to develop a model of the co-occurrence oflandslide causative factors. The output can be used either statistically or deterministically to develop a landslidesusceptibility map.The use of GIS is extremely important in both investigating and helping to establish the spatial relationshipsbetween causative factors and landslide events, and also in preparing map products of susceptibility, hazardand risk. For the first purpose, the development of spatial relationships, the GIS acts as an integrating frameworkfor the analysis. By providing a management system for the variety of input spatial datasets and the tools forinvestigating their interrelationships, the GIS can greatly improve the efficiency of such analysis. Table 5.1 listssome of the datasets relevant to landslide investigation that are available in Ireland.36
Data Theme Dataset Scale/Resolution CoverageSoil General Soil Map of Ireland 1:575,000 Whole CountryAFT county soil maps 1:126,720 Partial (44%)AFT soil survey field maps 1:10,560 scale Partial (44%)IFS County Soil Maps 1:50,000-1:100,000 NationalIFS County Parent Material 1:50,000 Nominal NationalMapsGeology GSI bedrock geology 1:100,000 NationalGSI groundwatermapping/Aquifer Table 5.1 Digital datasets of relevance to landslide hazard assessmentGSI geotechnical dataRemoteGSI quaternarySensingmappingGIS can be used to map the location of recorded landslide events, but importantly, it can also be used toElevation investigate EPA/Teagasc the occurrence DEM of events 20m which have not previously National been recorded. This investigation can use anumber OSI Contour of methods (Vector) including aerial 10m photo interval interpretation, satellite National image interpretation, satellite image classificationand OSI terrain DEM analysis. To date the use Mixed of these approaches, National which are broadly termed remote sensing methods,has GeoTOPO been somewhat DTM hampered by 1000m the resolution of the Whole available Country data (with the exception of aerial photointerpretation). Synoptics DTM However the increasing 50m development and Whole availability Country of commercial high resolution satelliteimagery with resolutions of 1 metre and less suggests that this area will become increasingly important in theLand cover future. CORINE The development 1990 of high resolution 25Ha terrain models, Whole particularly Country by acquisition technology such as LIDAR,will CORINE also potentially 2000 yield significant 25Ha gains in efforts to map Whole previous Country unknown landslide events. Table 5.2 listssensor IFS County data which Land can cover be of use for 1Ha landslide hazard assessment. NationalMapsClimate ICARUS (NUIM) 1961-90Baseline ClimatologiesMet Eireann observed datanetwork1000mWhole CountryAir photo1973 National1:30,000 NationalStereophotography1995 National1:40,000 NationalStereophotography1995 National 1:40,000 National37
Page 1 and 2: Landslides in IrelandGeological Sur
Page 3 and 4: LANDSLIDESinIRELANDEditorRonnie Cre
Page 5 and 6: CONTENTSPreface ...................
Page 7 and 8: Fig. 4.3 Forces caused by water in
Page 9 and 10: PREFACEUntil recently Ireland has b
Page 11 and 12: een very important in populating th
Page 13 and 14: involves a report on the current st
Page 15 and 16: Main Objectives• Increase public/
Page 17 and 18: 1. INTRODUCTIONRonnie Creighton1.1
Page 19: 1.3 The Landslides PublicationThis
Page 22 and 23: Peat flows are not nearly so well d
Page 24 and 25: In Ireland the Quaternary or uncons
Page 26 and 27: Journal - published papersLetter -
Page 28 and 29: Fig. 3.1 Two images showing the use
Page 30 and 31: Table 3.1 Landslide Events Per Coun
Page 32 and 33: Fig. 3.3 Location map of the Pollat
Page 34 and 35: 3.7.4 Quaternary GeologyQuaternary
Page 36 and 37: 3.8 The Derrybrien Landslide - 2003
Page 38 and 39: • The classification scheme shoul
Page 40 and 41: The force causing the block to slid
Page 42 and 43: Plate 4.1 Herringbone drainage syst
Page 44 and 45: 1210Number of events864Raised bogBl
Page 46 and 47: It is well known by research at Uni
Page 48 and 49: 5. LANDSLIDE SUSCEPTIBILITY MAPPING
Page 50 and 51: Two simplified hypothetical example
Page 54 and 55: Platform / sensor pixel resolution(
Page 56 and 57: For this initial run, the criteria
Page 58 and 59: 42Fig. 5.5 Peat and peaty podzols f
Page 60 and 61: for susceptibility mapping purposes
Page 62 and 63: elationships between developed susc
Page 64 and 65: The methodology used to derive the
Page 66 and 67: 50Fig. 5.12. Landslide susceptibili
Page 68 and 69: 52Table 5.6. Landslide classificati
Page 70 and 71: The percentage of events occurring
Page 72 and 73: with slope, overall 20-25% of all e
Page 74 and 75: As the dataset was not available at
Page 79 and 80: CHAPTER 5.2 - TABLE APPENDIXBedrock
Page 81 and 82: 6. LANDSLIDES AND PLANNINGAileen Do
Page 83 and 84: 6.2.4 Development ManagementThe phy
Page 85 and 86: 6.5 Current Practice on Landslides
Page 88 and 89: 7. LANDSLIDES IN NORTHERN IRELANDTe
Page 90 and 91: 2. MudflowsPlate 7.1 Rotational Lan
Page 92 and 93: 7.2 Carboniferous Cliff Lines (Co F
Page 95 and 96: 8. RESEARCH ON IRISH LANDSLIDESKoen
Page 97 and 98: 8.4 Research. Post-2003 AbstractsTa
Page 99 and 100: Identifying, recognizing, and predi
Page 101 and 102: In the case of vulnerability mappin
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Steep slopes in glacial tillMichael
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9. RECOMMENDATIONS FOR FUTURE WORK9
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Priority 1 Peat slides and peat str
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TEXT REFERENCESAcreman, M., 1991. T
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Skipper, J., Follett, B., Menkiti,
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APPENDIX 2Glossary of TermsBlanket
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APPENDIX 3Nomenclature for Landslid
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APPENDIX 4101
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103
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105
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Hammond, R. 1979. The Peatlands of
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APPENDIX 7Useful Web Linkswww.gsi.i
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