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