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Part 14
NEW HIGH-TECH
TOOLS FOR
IDENTIFYING
LANDSLIDE FEATURES
• Digital map image of the West Lost Trail Creek
Landslide created by overlaying USGS DOQQ
aerial photo on 10 m Digital Elevation Model,
then rotating in space, using ArcGIS 9.1
Synthetic Aperture
Radar (SAR)
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SAR has ability to see through
clouds and woody vegetation,
up to about 4 inches thick.
It provides acute vertical
exaggeration of geomorphic
features, crucial to landslide
hazard mapping
Image resolution and density
controls scale of mappable
features, such as these debris
lobes
LiDAR
Light Detection and
Ranging
• LiDAR image of
Paine Run, Virginia
revealed an active
fault scarp never
previously seen,
mapped, or even
imagined!
• “Bare Earth”
assessment has
incredible potential
for landslide
mapping
Seattle/Toe Jam Hill Fault
Zone
• Another
USGS LiDAR
imaging
project that
revealed
hitherto
unmapped
Holocene
fault scarps
• Common
problem in
wooded
terrain
Topographic Algorithms
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Algorithms allow for rapid screening of large land areas,
when combined with neural networks to create an artificial
intelligence (AI) program to enable discriminate mapping.
Accuracy depends on quality and scale of digital elevation
models
Will supplant stereopair aerial photographic methods for
reconnaissance mapping of potential landslide hazards
Limitations would be spelled out on map products,
recommending site-specific investigations be employed
to determine presence, depth and character of past
landslippage.
Property would not be “condemned” unfit for
development solely on interpretation of the regional
hazard map.
Recent USGS Landslide Maps
The USGS has used San Mateo County, CA as their
prototype hazard mapping area since 1969. These plots
show debris flow hazard map (at left) and landslide
incidence map (at right) for Montara Mountain area of
northern San Mateo County, CA.
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End Users will demand increasingly detailed assessments.
Landslide hazard maps generated using GIS can be overlain on
tax assessor parcel maps will be used like FEMA Flood Insurance
Rate Maps, spreading risk to lenders and insurers.
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Future map products will appear like this, overlaying
map information on DEMs and digital color images.
These products relate well to the general public,
planners, and decision makers. ArcGIS 9.1 product.