Image credit: Natural Resources Canada
Slope instability can be a significant geohazard and is not limited to high relief areas. Low angled slopes can also be subject to slope instability, especially when disturbed, loaded or excavated and/or changes occur to drainage/groundwater condition. Impacts from slope instability can have high costs to development and operations, potentially resulting in disruption to operations, loss of access and significant Health, Safety and Environment (HSE) implications.
Slope instability is a function of many factors (including: slope angle; rock/soil type; geomorphic setting; water/groundwater; climate; vegetation; geological history; and anthropogenic influences). Slope maps are frequently generated from a Digital Elevation Model (DEM) to show areas of steep slopes of assumed highest hazard. High quality DEMs can be derived from EO images (see the Elevation product sheet); however, factors other than slope alone should be considered in assessing slope stability (e.g., landslide type: creep, deep-seated landslide, debris flow, rockfall, etc.; proximity of project infrastructure; and infrastructure susceptibility to debris run-out).
DEM analysis can be undertaken at multiple scales, responding to needs from regional level information down to detail need for planning infrastructure siting (facilities, pipelines, etc.). DEM analysis may include slope mapping, aspect mapping and shaded-relief analysis to identify slope instability.
Multispectral analysis can be used to distinguish variations in soil, rock and groundwater and identify landslide scars in heavily vegetated regions. Multi-temporal analysis (utilising archive data together with recent imagery) can help estimate distribution and frequency of slides in an area, and expected run-out distances.
The slope stability product delivers quantitative landslide susceptibility hazard and risk mapping and reporting. Stability value coded areas (raster) can be produced from the derived stability models. Delineation of unstable versus stable areas can also be provided (polygon vectors) along with text reports elaborating on the nature of problem areas.
Known restrictions / limitations
Geographies with dense vegetation such as tropical regions reduce the accuracy of interpretation. Use of radar imagery can mitigate these limitations to some extent.
Lifecycle stage and demand
Pre-License: Information on geomorphology and slope instability to support decision-making on a prospect with relation to cost estimation for exploration and development costs associated with access and geohazards.
Exploration: Information to support geomorphological mapping, terrain analysis and hazard identification, in particular to assist planning of seismic surveys and other field work.
Development: Information for planning and design of infrastructure, to support site selection and pipeline routeing to determine hazards and risks in a proposed development area.
Production: Monitoring hazards within project area that may affect operations.
Decommissioning: Not typically required unless ongoing monitoring is required.
Geographic coverage and demand
Coverage is global.
Demand is global.
Demand is in all terrain areas.
OTM:036 Geohazard exposure analysis
OTM:060 Forecasting landslide locations
Input data sources
Optical: VHR1, VHR2, HR1, HR2
Radar: VHR1, VHR2, HR1, HR2, MR1
Archive data has considerable value to show multi-temporal changes over decades to help identify and quantify active geomorphic processes including slope instability.
Spatial resolution and coverage
Varies depending on input imagery used and client needs.
Low resolution DEM for basin wide exploration studies, higher resolution DEM and optical imagery (30 m to less than 1 m) for development and infrastructure planning and design.
Minimum Mapping Unit (MMU)
Variable, depending on source data resolution and project requirements.
Accuracy / constraints
Varies depending on input imagery and user requirements.
Thematic accuracy: 80-90% in areas of low vegetation cover and density.
Spatial accuracy: The goal would be 1 pixel, but depends on reference data.
Accuracy assessment approach & quality control measures
Professional judgement by comparison with any published geological/geomorphological mapping or reports.
Field reconnaissance mapping and verification.
Frequency / timeliness
Varies depending on user requirements.
Observation frequency: Subject to project requirements. Monitoring of landslide prone areas may be undertaken at regular defined intervals, possibly related to season.
Timeliness of delivery: Usually off-the-shelf data can be utilised. Commissioned data may be required in some cases e.g., for collection of VHR1 stereo data for high resolution DEM production.
Availability from commercial suppliers and other agencies.
New acquisitions can be requested globally for higher resolution data.
Archives products available for public search.
Delivery / output format
Hatfield coonsultants /Arup
# of Pages:
Internal – Project consortium and science partners
External – ESA
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