Transcript Field- And GIS-Based Measurements of Coastal Change for the Southeast Chukchi Sea, Alaska William F.

Field- And GIS-Based Measurements of Coastal Change
for the Southeast Chukchi Sea, Alaska
William F. Manley
Diane M. Sanzone
James W. Jordan
Owen K. Mason
Eric G. Parrish
Leanne R. Lestak
INSTAAR, University of Colorado
Arctic I&M Program, National Park Service
Dept. of Environmental Studies, Antioch University New England
GeoArch Alaska
INSTAAR, University of Colorado
INSTAAR, University of Colorado
AGU Presentation -- December 14, 2006
See also: instaar.colorado.edu/QGISL/ARCN/
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Coastal Erosion
 Rapid, observable change to the
environment
 Multiple impacts on a variety of habitats
 Fragile coast is a sensitive indicator of
“stressors”:
 direct human disturbance
 climate change:
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longer ice-free season
increased permafrost melting
change in frequency and intensity of storms
sea level rise
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Goals
 Field measurements as test of GIS approach
 Preliminary GIS results
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Study Area
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Coastal Monitoring Stations
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27 sites
first established 1987-1994
revisited in 2006
measured on “bluff top”
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Field Methods
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Remote Sensing & GIS Approach
 High-resolution base imagery
2003
• 2003 orthophoto mosaic
 Historic aerial photographs
ca. 1980
• orthorectified photos for ca. 1980
• orthorectified photos for ca. 1950
 Comparison of different “time slices”
allows us to detect and measure change
ca. 1950
 Imagery and data useful for other concerns
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• from NOAA & NPS 1:24,000 natural color photos
• mosaic created by Aero-Metric
• 0.6 m resolution
• accuracy: 1.2 m (RMSE)
• 112 tiles, 98 GB: lots of imagery!
• highest res. in Alaska for this large of an area
• available to the public early 2007
• valuable for other types of research
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frames
5760frames
ColorIR
IR
Color
1.0 m res.
1:64,000
1.0 m resolution
1.5 m accuracy (RMSE)
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130frames
frames
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Blackand
& White
Black
White
1.0 m res.
1:43,000
1.0 m resolution
2.0 m accuracy (RMSE)
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Shoreline Reference Feature (SRF):
“bluff top” (wave-cut scarp)
Barrier island or spit
Mainland bluff
Beach ridge complex
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2003
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1949
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1985
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2003
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1949
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1985
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2003
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DSAS
Thieler et al. (2005)
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Baseline
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Transects
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Transects
51.4 m
÷ 36 yr =
1.4 m/yr
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“Early” Period
ca. 1950 – ca. 1980
m/yr
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“Late” Period
ca. 1980 – 2003
m/yr
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GIS Errors
Shoreline Position (m)
ca. 1950 ca. 1980
Orthorectification
Digitizing
Total (SRSS)
2003
2.0
1.5
NA
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3.6
4.3
3.0
Coastal Change
“Early”
“Late”
ca. 1950 – ca. 1980 ca. 1980
2003
“Long Term”
ca. 1950 2003
Position (m)
5.6
5.2
4.7
Rate (m/yr)
± 0.20
± 0.23
± 0.09
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r2 = 0.80
n = 21
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mean
difference:
0.12 m/yr
r2 = 0.80
n = 21
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GIS Errors
Shoreline Position (m)
ca. 1950 ca. 1980
2003
Orthorectification
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1.5
NA
Digitizing
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3.6
4.3
3.0
Total (SRSS)
Coastal Change
“Early”
“Late”
ca. 1950 – ca. 1980 ca. 1980
2003
“Long Term”
ca. 1950 2003
Position (m)
5.6
5.2
4.7
Rate (m/yr)
± 0.20
± 0.23
± 0.09
Field Test
Rate (m/yr)
(mean difference)
± 0.12
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• spatial variability
• “early” erosion
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• accretion
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• station eroded
• “late” erosion
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“Early” Period
ca. 1950 – ca. 1980
CAKR (n = 1628)
Avg ± SD
ca. 1950 – ca. 1980
0.0 ± 1.1
ca. 1980 – 2003
-0.5 ± 0.6
BELA (n = 1146)
Avg ± SD
ca. 1950 – ca. 1980
-0.6 ± 0.4
ca. 1980 – 2003
-0.2 ± 0.3
xy plot
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“Late” Period
ca. 1980 – 2003
CAKR (n = 1628)
Avg ± SD
ca. 1950 – ca. 1980
0.0 ± 1.1
ca. 1980 – 2003
-0.5 ± 0.6
BELA (n = 1146)
Avg ± SD
ca. 1950 – ca. 1980
-0.6 ± 0.4
ca. 1980 – 2003
-0.2 ± 0.3
xy plot
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Is coastal erosion increasing
with Arctic warming?
xy plot
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Conclusions
 Field:
• more precise
• measurements more often
 GIS:
• acceptably low errors
• comprehensive spatial analysis
 Is global warming responsible?:
• storm climatology important
• high spatial and temporal resolution needed
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