Lab 8 - Damage Assessments

The last lab! This week finished up the last lab in GIS Applications and the focus was on conducting damage assessments after natural disasters using a GIS. Our readings for the week primarily covered water based natural disasters like tsunamis and hurricanes but I think some of the tools used could be applied to other things like earthquakes and tornadoes too. Hurricane Sandy was the topic for the final lab with an in depth look at several blocks in a  town in New Jersey. We used pre-event and post-event images to assess the damage in a three block study area in ArcMap. The first step was to set up a geodatabase and populate it with the different features that would be useful in conducting a damage assessment like county boundaries, property lines, and raster image mosiacs. Once all of the data was set up I moved on to the analysis.

I created a new point feature class to annotate the damage to buildings in the study area. The first thing I did was add one point to each land parcel each using the pre-storm imagery as a reference. I accidentally added multiple points on a few parcels when I first started as I went back and forth between attributes and creating features so I decided to add all of the points first. Then to identify the damage I zoomed in to 1/3 of a block at a time and used the Flicker Tool on the Effects Toolbar to go back and forth between pre and post storm imagery. (The Flicker Tool is great and i wish knew about it sooner. The tool lets you lift up the top layer and look beneath it without having to wait for the whole image to reload, almost like lifting the corner of a newspaper to look at the next page.) Some of the damage was very easy to identify and categorize because the buildings were completely gone but other areas were more difficult. 

Post-event image of study area with structure damage categories, original coastline and 100m, 200m, and 300m markers

From looking at the study area as a whole and then looking at the zoomed in view there appeared to be sand covering everything that was previously pavement or grass. Due to the sand movement I considered every parcel inundated and every structure at least “Affected”. Shadows made it difficult to discern how much damage occurred on some parcels so I looked at the surrounding properties to help estimate the amount of damage. I could not tell if all of the displaced items and buildings moved due to water flow or wind so I also considered every parcel with a vertical structure at least “Affected” by wind if not worse.  Buildings with roof damage were given a higher wind damage rating. Buildings that were completely destroyed were only given a wind rating of “Affected”. Wind damage was the most difficult category to evaluate. 

My results for the three block study area are in the table below.

Structural Damage Category	Count of Structures Within Distance Categories from Coastline
	0-100m	100-200m	200-300m
No Damage	0	0	0
Affected	4	0	5
Minor Damage	0	2	20
Major Damage	1	28	21
Destroyed	7	10	0
Total	12	40	46