This document summarizes a GIS analysis of landslides near Rocky Mountain National Park, Colorado. The analysis used GIS tools to identify factors associated with slope mass movements after heavy rainfall in 2013. Results showed that landslides commonly had multiple source areas and lithologies. Specifically, south-facing slopes between 30-60 degrees, granite rock type, and slopes made up the largest percentages and areas of landslide sources. Proximity to rivers was not a major cause of landslides in this area.

1. GIS Analysis of Landslides Near Rocky Mountain National Park, Colorado
Connor Newman
Department of Geological Sciences and Engineering
GIS I
Landslides
are
an
important
geomorphic
process
which
have
the
capability
to
affect
both
human
and
natural
systems.
Landslides
and
other
slope
mass
movements
can
be
a9ributed
to
a
number
of
factors
including
slope
angle,
aspect,
and
rock
type.
During
September
2013
the
Front
Range
area
of
Colorado
received
an
extreme
amount
of
rainfall,
this
precipitaGon
and
subsequent
flooding
caused
numerous
mass
movements
in
the
region.
The
area
south
of
the
town
of
Estes
Park,
on
the
edge
of
Rocky
Mountain
NaGonal
Park
was
one
of
the
most
impacted
areas.
Numerous
landslides
occurred
at
a
variety
of
scales
,
and
the
causaGve
factors
involved
in
these
landslides
has
not
yet
been
determined.
IntroducGon
Study
Area
Methods
Results
Conclusions
References
Cited
Figure
1:
Map
of
study
area
with
Colorado
map
shown
in
inset.
The
current
study
area
(seen
in
red
on
Figure
1
inset)
is
located
on
the
north-­‐western
extent
of
the
Colorado
Front
Range
(seen
in
blue
on
Figure
1),
the
most
heavily
populated
area
of
Colorado.
The
study
area
contains
three
main
lithologies
with
differing
strength
characterisGcs;
granite,
gneiss,
and
glacial
driV.
The
study
area
also
contains
a
wide
variety
of
slope
aspects
and
angles.
GIS
analysis
was
performed
in
order
to
determine
what
factors
were
associated
with
the
majority
of
slope
mass
movements.
GIS
tools
and
skills
uGlized
were:
digiGzing
polygons;
geodatabase
feature
class
and
feature
dataset;
aspect;
slope;
clip
raster;
mosaic
raster;
model
builder;
reclassify;
raster
to
polygon;
buffer
line;
and
intersect.
Number
Area
(km2)
%
Area
Total
Landslides
21
0.648
N/A
Landslide
Sources
39
0.097
15
River
100
m
Buffer
1
0.007
1.1
South
Facing
Sources
37
0.055
56
30-­‐60
Degree
Slope
Sources
37
0.068
70
Granite
Sources
35
0.082
84
Glacial
DriK
Sources
2
0.005
5.2
Gneiss
Sources
2
0.011
11
Figure
3:
Processing
example
showing
several
layers
created
from
DEM
raster.
Figure
2:
Processing
steps
involved
in
idenTfying
landslide
mechanism.
Figure
4:
Map
displaying
complex
nature
and
mulTple
source
points
of
landslides
in
north
St.
Vrain
Canyon.
Results
from
GIS
analysis
has
idenGfied
the
primary
causes
of
all
21
landslides
idenGfied
in
the
study
area.
Results
show
that
landslides
commonly
have
mulGple
source
areas,
can
be
sourced
from
mulGple
lithologies,
and
can
display
complex
geometries.
Findings
of
probable
causes
for
landslides
are
summarized
below.
-­‐South
facing
slopes
and
slopes
between
30
and
60
degrees
contained
the
same
number
of
landslide
source
areas,
though
source
areas
on
30-­‐60
degree
slopes
were
larger.
-­‐Granite
is
the
lithology
which
most
commonly
contributes
to
landslides.
Granite
also
made
up
the
largest
percentage
of
landslide
source
area.
-­‐Proximity
to
rivers
was
not
a
major
cause
of
landslides.
Figure
5:
Large
landslide
on
Twin
Sisters
Mountain
sourced
from
a
combinaTon
of
granite
and
gneiss.
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H.,
Derek
MarTn,
C.,
&
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C.
H.
(2007).
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