Monday, July 17, 2017

GIS 5100 - Lab 7 - Coastal Flooding

This weeks lab focused on Coastal Flooding and predicting the impact of sea level rises or storm surges.  The two part lab covered Hawaii in Part A and Florida in Part B.  

Our task in Part A was to concentrate on the District of Honolulu and use 2010 Census data to report population density and demographics of the areas affected or not affected by a 3 foot and 6 foot rise in sea level.  The map below answers the question, what is the population density in areas with flooding due to a 6 foot rise in sea level.  The map shows the flood depth in the impacted census tracts.  Looking at the table one can see that the coastline of Honolulu where there are likely expensive high rise condominiums or hotels and therefore less owner-occupied housing units with higher non-native or white populations is most vulnerable to sea level rises.  

What is the population density in areas with flooding due to a 6 foot rise in sea level?


Variable                 Entire District   3 feet Scenario              6 feet Scenario
                                                      Flooded   Not-flooded   Flooded   Not-flooded 
Total Population      390,738             8,544        382,194         60,005     330,733

% White                     19.48              36.79        19.09             29.58       17.64

% owner-occupied  48.98                 32.22        49.36             36.97       51.16

% 65 and older        18.13                7.41         18.14              17.18       18.30

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This part of the lab was labor intensive with several table joins and statistical analysis.

Part B focused on Collier County, Florida and was a comparison of two different DEMs of the same area, a Lidar DEM and a USGS DEM.   I think naming this a USGS DEM is misleading as USGS has data from Lidar as well.  I think the USGS DEM is from the National Elevation Dataset with a 1 arc-second ~30 meter resolution.  Regardless, Part B's coastal flooding analysis showed how important image resolution is when selecting a DEM to predict sea level rise or storm surge impact.  The reliability of the USGS DEM was much weaker than the Lidar DEM as born out in our % omisson and % commission calculations.  The Lidar image had a cell size of 25 sq. ft and the USGS image had a 100 sq. ft. cell size.

Both Part A and Part B took me much more time than the 7 hours described in the assignment.  Partially because I'm interrupted a lot while working on assignments but this lab was definitely more time intensive for me.

It was also coincidental that in the news this week, both locally and nationally, there were articles regarding coastal flooding and rises in sea level.

http://gatehouseprojects.com/risingseas/home/site/nwfdailynews.com

http://www.sfgate.com/bayarea/article/Marin-San-Mateo-County-sue-big-oil-over-climate-11294549.php

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