Advanced Topics in GIS

Natural Hazards Landslide Susceptibility

Modeling Landslides What factors influence landslides? What data can be used to model landslides susceptibility and what are we going to use? What analyses can suggest probabilities of landslides? What is ModelBuilder and how can it be used to model landslides How can the results be visualized in 3D

Factors Influencing Landslide Susceptibility Real-world data and techniques Analyses to Determine –Slope – steeper more susceptible –Aspect – South facing = dry, little vegetation –Burn Severity – least vegetation as severity of burn increases –Weigh each output’s affect to determine areas with highest susceptibility

Our Analysis Will Use Raster –“pixels” –a location and value –Elevation of study area hIllshade of elevation –DRG of study area Vector –Lines & Polygons –“Features ” Roads, Streams, Faults, geology, burn severity Real world

Basic Data Sets for Our Model Raster –Elevation data (DEM) Continuous data set with each center of a grid containing the value for the elevation (10 x 10 m grid, Z in meters) –Digital Raster Graphic of study area Vector –Severity of burn –Road, streams, faults, geology, historic landslides Vector to Raster Conversion –Severity of burn from Vector (polygon) to raster

Four Vector and One Grid Data Layers Faults LayerStreams Layer Landslide Layer Roads LayerDEM Layer

High Landslide Susceptibility

Grids – Layers can be “Combined” - binary suitability models Use for simple problems – Map Algebra or Boolean And Tools Classify layers into good (1) and bad (0) – Combine with AND, addition or multiplication: [ski] = [snow] & [slope] & [sun] Advantages: – Easy Disadvantages: – No “next–best” sites – All layers have same importance – All good values have same importance Slope Sun Ski Snow

Weighted suitability models Use for complex problems –Use tool from Spatial Analysis Toolbox Classify layers into suitability 1-9 (9 = best) – Weight and add together: Ski = ([snow] *.5) + ([slope] *.3) + ([sun] *.2) Advantages: – All values have relative importance – All layers have relative importance – Returns suitability on a scale 1-9 Disadvantages: – Preference assessment is harder Sun Ski Slope Snow

Using Tools in ArcToolbox – one by one to carry out analysis

Modeling What factors influence landslides? How can data be used to model landslides susceptibility? What analysis can yield probabilities of landslides? What is ModelBuilder and how can it be used to model landslides

Automating Analysis – ModelBuilder... And Shared

Landslide ModelBuilder

Project Format – Additions Folders – simple File Geodatabase –Need to add this to the exercise Add Remote Sensing aspect –Change detection –Define past to recent slides –Continued Forest oversight –Use GPS to ground truth and reference RS

Complete the Landslides exercise handout for Part II Understand your data (Demo) Use the Tools in the ToolBox (Demo) – Part I of exercise Create a ModelBuilder model – you complete this using guide Use the results in a 3D animation – if time permits