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Interpreting Landscape to Predict Landslide Vulnerability A brief overview of the techniques involved to evaluate the conditions for a landslide Christopher Bride GEP635 Spring 2012 Prof. Yuri Gorokhovich Photo courtesy of Riverkeeper.org

Landslide Susceptibility Evaluation Techniques

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A GIS analysis of landslide characteristics that contribute to the chance of a landslide occurring.

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Page 1: Landslide Susceptibility Evaluation Techniques

Interpreting Landscape to Predict Landslide Vulnerability

A brief overview of the techniques involved to evaluate the conditions

for a landslide

Christopher BrideGEP635Spring 2012Prof. Yuri Gorokhovich Photo courtesy of Riverkeeper.org

Page 2: Landslide Susceptibility Evaluation Techniques

Study Site: Milton, NY

Page 3: Landslide Susceptibility Evaluation Techniques

Milton Landslide into the Hudson River

Page 4: Landslide Susceptibility Evaluation Techniques

Slope Profile via Google Earth

Page 5: Landslide Susceptibility Evaluation Techniques

Parameters to Study

• Slope • Soil type• Tree/vegetation cover• Many others outside the scope of this class– Hydration– Impermeable surface– Other man-made factors

Page 6: Landslide Susceptibility Evaluation Techniques

GIS• DEM files: Digital

Elevation Model• GIS Clearinghouse• County boundaries• Hudson River

shoreline shapefile

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Data acquisitionGrid enables easy location of the tiles needed to acquire for this project

Also can be done by town name.

Download, unzip, add to map, symbolize via “stretched value”, “discrete colors”, or “classify”

Page 8: Landslide Susceptibility Evaluation Techniques

Digital Elevation ModelColored to indicate elevation in feet

This is actually 4 grid tiles

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Analyze slope: Geoprocess/Slope

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Soil Analysis

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Simplified: Dangerous types vs. everything else

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Slope & Soil Type

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Slope & Soil Type

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Orthophotos: Tree/Vegetation cover

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Data Acquisition

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Download Ortho-index grid

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Input Ortho-grid into GIS

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What tile do I need?Choose “ID” tool in ArcGISSelect the grid position you needRecord or memorize the grid number

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Find tile coordinate in list, download/unzip, and add to map

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Start combining layers• Ulster County Orthophotos underneath Slope

Analysis

Page 21: Landslide Susceptibility Evaluation Techniques

Milton Landslide & Slope

Landslide Area

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Landslide Site & Soil TypeGlacial Deposits

Bedrock (type “r”)

“other”

Landslide Area

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Slope & Soil Type

Landslide Area

Page 24: Landslide Susceptibility Evaluation Techniques

Index/Model

• Landslide susceptible soils categorized into one class • Landslide susceptible slopes categorized into one

class (slopes >30 degrees)• Vegetation coverage was not on hand, but would

have otherwise been given a classification as well • For now, we will look at where soil type and

landslides overlap/intersect.• Then use GoogleEarth or orthophotos to evaluate

vegetation coverage.

Page 25: Landslide Susceptibility Evaluation Techniques

Union of Slope and Soil Type LayersNeed to convert slope raster into a polygon so that a Union geoprocess can be performed with the Soil layer

Page 26: Landslide Susceptibility Evaluation Techniques

Slope Raster to PolygonSlope Raster from DEM Slope polygon file >30o

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Union these two layers for Landslide susceptibility analysis

Slope polygon Soil polygon

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Soil and Slope UnionAfter “Union” geoprocess, the areas with >30 degree slope that overlay the landslide susceptible soil types are indicated in red. All other areas, soil and slop alike, are indicated in green.

Page 29: Landslide Susceptibility Evaluation Techniques

Ulster Landslide Area Analysis

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Landslide site, 2011

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Final map

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Potential Problem AreaResidential, tree removal apparent, strong slope and soil type correlation to landslide conditions.

Advice? Don’t remove the trees or vegetation in these areas.

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GoogleEarth Photo of Potential Landslide Area

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References

• Orthophotos and Soil Data: http://gis.ny.gov/ (NYState GIS Clearinghouse)

• Digital Elevation Models: http://cugir.mannlib.cornell.edu/datatheme.jsp?id=23 (CUGIR: Cornell University Geospatial Information Repository)

• Opening photo: http://hudsonriverkeeper.blogspot.com/2012/04/landslide-into-wetland-at-residential.html

Page 35: Landslide Susceptibility Evaluation Techniques

Thank You!