Geohazard Evaluation and Constraint Mapping on a Regional Scale: a Practical Approach for Linear Infrastructure Projects
Modern routing for pipelines is generally based on assessment of various technical, environmental and social constraints. Guided by terrain characteristics, two general approaches may be applicable: (i) centerline method, when one or only a few constraints limit the route selection option, and ii) constraint mapping, when areal and regional constraints comprise selection criteria that have to be evaluated (Sweeney, 2005). With respect to the latter, regional geohazard mapping is a crucial task especially in the early project phases. Since geohazards, especially landslides, but also erosion, karst, active faults and permafrost conditions may pose severe contraints for the structural integrity, comprehensive evaluation of terrain features should be state of the art. Due to the often large spatial extents of the corridors (several 1,000 km2) and strict time limits, detailed site investigations and local monitoring are hardly practicable. Thus, terrain mapping requires a practical approach with a systematic workflow. For geohazard evaluation mainly heuristic approaches are applied, based on i) geological field surveys, ii) analyses of geological and topographical maps and iii) “standard” remote sensing data, i.e. multi-temporal airborne and satellite images. In many regions, monitoring data and reliable chronicles on geohazards are not available. Airborne laser scanning (LiDAR) data are also not always available on a regional scale and thus have to be aquired project-specifically, i.e. often for selected centreline corridors only. In landslide-prone (e.g. flysch badlands, volcanoclastic and soft rocks) and hardly accessible terrain, regional analyses based on satelliteborne radar interferometry (InSAR) may provide further and objective information on terrain (in )stability, and help to establish geohazard inventory maps (landslides, erosion, active faults, subsidence). Based on engineering geological experiences gained from major pipeline projects in different geological and morphological settings (Europe, Asia), a classification scheme of terrain features and associated geohazards displaying the resulting constructional and residual risks is proposed.