Interpreting Landscape to Predict Landslide Vulnerability A brief overview of the techniques involved to evaluate the conditions for a landslideChristopher BrideGEP635Spring 2012Prof. Yuri Gorokhovich Photo courtesy of Riverkeeper.org
Parameters to Study• Slope• Soil type• Tree/vegetation cover• Many others outside the scope of this class – Hydration – Impermeable surface – Other man-made factors
GIS• DEM files: Digital Elevation Model• GIS Clearinghouse• County boundaries• Hudson River shoreline shapefile
Data acquisitionGrid enables easylocation of the tilesneeded to acquire forthis projectAlso can be done bytown name.Download, unzip, addto map, symbolize via“stretched value”,“discrete colors”, or“classify”
Digital Elevation ModelColored to indicate elevation in feetThis is actually 4 grid tiles
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.
Union of Slope and SoilType LayersNeed to convert slope raster into apolygon so that a Union geoprocesscan be performed with the Soil layer
Slope Raster to PolygonSlope Raster from DEM Slope polygon file >30o
Union these two layers for Landslide susceptibility analysisSlope polygon Soil polygon
Soil and Slope UnionAfter “Union” geoprocess, the areaswith >30 degree slope that overlay thelandslide susceptible soil types areindicated in red. All other areas, soiland slop alike, are indicated in green.