Week 4: Damage Assessment

Damage Assessment of structure on East New Jersey
coast after Hurricane Sandy

This weeks lab involved damage assessment of structures near the New Jersey Coast after Hurricane (super storm) Sandy in Fall 2012.  Damaged structures in this case were homes and businesses that were inundated or wind-ravaged.  We compared pre- and post-Sandy aerial imagery of our study area and visually determined the severity of damage (see image top-right; description below).  Then, we regressed the severity of structure damage on the distance from the coastline in intervals of 100 meters (e.g., 0-100m from coastline, 100-200m, etc.; see table below).

I first coarsely assessed the entire affected area using pre- an post-Sandy aerial imagery.  This visual assessment included areas outside the delineated study area that were highly affected, as well as areas that appeared almost entirely unaffected.  This was done to make my damage assessment more objective.  Based on this broad-scale approach, I determined that the study area was one in which structure damage was highly variable – some properties were destroyed completely, while some looked unharmed.  Further a majority of destroyed structures were located in the easternmost region of the study area.

The general process of identifying the structural damage for each parcel was a left to right sweep of each block.  This allowed sufficient detail without taking hours to process a small area.  I primarily used the ‘slide’ effect tool to compare the two aerial images of the pre- and post-Sandy study site. If a structure was clearly moved from its original foundation or was leveled, then I chose to label it as destroyed.  Some structures were absent all together, those were labeled as ‘destroyed’ as well.  If a structure had major collapse, which was noticeable from aerial imagery by debris or a change in shape, then it was labeled ‘major damage’.  'Minor damage' was subjectively decided to describe a home that was generally surrounded by other severely affected homes, but was not obviously damaged from imagery.  ‘Affected’ was given to any home that appeared to have debris in the yard, which I presumed to be material from the structure.  A structure was labeled ‘no damage’ if it appeared generally identical in shape to the pre-Sandy imagery, and was surrounded by other homes which appeared unharmed.  This was based on the assumption that adjacent homes protected those upwind and uphill of the storm.

Structural Damage Category	Count of structures within distance category
	0 – 100 m	101 – 200 m	201 – 300 m
No Damage	0	1	7
Affected	0	9	24
Minor Damage	0	16	6
Major Damage	0	8	4
Destroyed	12	6	4
Total	12	40	45