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 Layer Streams Layer Landslide Layer
Roads Layer DEM 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
10
00
1
0 0
1
00 1
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
95
1Sun
Ski
96.6
7.01.8
5.04.2
9
51
Slope
95
1
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. . . 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
http://seamless.usgs.gov/; http://seamless.usgs.gov/; http://www.census.gov/geo/www/tiger/http://www.census.gov/geo/www/tiger/
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