Lab09
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California Polytechnic State University, San Luis Obispo *
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218
Subject
Geography
Date
Dec 6, 2023
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docx
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Uploaded by MinisterEchidnaPerson2138
Raster Analysis
Sea Level Rise around Humboldt Bay
Deepak Tripathi || October 29
th
, 2021
Methodology
The Digital Elevation Model (DEM) data and County outline data for the Humboldt County is
projected in ArcGIS Pro. The primary task for this lab was to create rasters representing the land that
might be inundated by water as the level of the ocean rises. Using the ‘Raster Calculator’ tool in
ArcGIS Pro analysis of on entire raster images was done group the various land parcels as per there
usage, such as public land, agriculture land and etc. Further the land inundated due to sea level rise
at four stages was done, i.e, land inundated when sea level rise by 1 meter, 2 meter, 5 meter and 10
meter.
To find the area in hectares the number of pixels in the raster are converted to meters squared by
multiplying the number of pixels with 0.008035. Reclassify tool in spatial analysis was used to create
map that shows the various levels of sea rise and the desired maps where produced.
Result
Following the above state methodology the following maps where created:
1
Figure 1: Land indicated below 1m
2
Figure 2: Land indicated below 2m
3
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Figure 3: Land indicated below 5m
4
Figure 4: Land indicated below 10m
5
Figure 5: Flood Risk Zone
The Figure 5 illustrates the arear under flood risk with rise in sea level at 5 stages. Table 1 explains
these five sea level rises.
Table 1: Legends for figure 5
Sea level rise
Legend Value
Sea level rise by 1 meter
1
Sea level Rise by 2 meter
2
Sea level Rise by 5 meter
3
Sea level Rise by 10 meter
4
Sea level Rise by 943 meter
5
Table 2 represents the land area Land area inundated by rise in sea level.
Table 2: Land area inundated by rise in sea level
S.No.
Type of Land Parcel
Area Inundated by seat level rise (Hectare)
1 meter rise
2 meter rise
5 meter rise
10 meter rise
1
City
34.952
594.550
1477.894
1973.605
6
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S.No.
Type of Land Parcel
Area Inundated by seat level rise (Hectare)
2
Agriculture
21.285
2841.120
9474.269
13246.461
3
Residentail
3.383
24.659
289.839
841.369
4
Commercial
0.177
4.773
37.556
57.169
5
Industrial
5.962
79.386
252.918
559.863
6
Recreational
50.371
1117.910
1825.713
2354.536
7
Tribal
0.129
0.305
0.779
1.519
8
Public
3.801
56.647
287.147
532.825
9
Other
0.860
9.184
73.810
194.246
Total Area
120.919
4728.533
13719.923
19761.592
Conclusion
After the generation of the final map, analysis to assess the viability of the site was done and
the following observations where made:
1.
The area near the bay and costliness of Eureka city are at very high risk and would be flooded
with a sea level rise of one meter.
2.
As we move always from the bay and the coast line the risk of flooding decreases.
3.
For more accurate data and risk assessment, further studies with correlation to sea level rise
in rainy season could be done.
4.
The population in zone 1 and 2 need to be educated and prepared about the risk involved
with sea level rise.
Acknowledgement
I would like to thank Professor James Graham and the Humboldt State University for
providing the ArcGIS Pro software used for creating this report and I would like to thank all the
institutions which have provided data on public platforms and where used in this report and cited
below.
7
Appendix A
Question 1:
List the "Pixel Type," "Pixel Depth," and "Cell Size" for the DEM.
Answer:
Pixel type
Floating point
Cell size
X=8.96409536744432
y=8.96409536744424
Pixel depth
32 bits
Question 2:
How much land appears to be between 0 and 1 meters? You may need to zoom in and
toggle between the two layers to see the pixels that are between 0 and 1.
Answer:
The arear of land between 0 and 1 meter is approximately 272 hectares.
Question 3:
Zoom in to an area of Arcata and examine the differences between the raster and
polygon version of the parcel layers. What impact do you think this difference will have on the
analysis?
Answer: The polygon file has better resolution when compared to the new raster file also the
polygon file is faster to load on ArcGIS Pro when compared to the newly created raster file. A change
in the tolerance level can be observed when comparing polygon data to rater data. These factors can
impact the results when analyzing the rise of sea level.
Question 4:
What "Pixel Type" is the new raster?
Answer: The new raster is an ‘
unsigned char’ type with 4 bit pixel depth.
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