GIS 5100 - Lab 8 - Damage Assessment

In this multipart lab, we were tasked with performing a damage assessment based on imagery from before and after Hurricane Sandy.  The first phase was to create a map of the path of Hurricane Sandy in order to have a background.  We learned how to create our own marker symbols.

Tracking of Hurricane Sandy, 2012

The next step was to prepare data by creating a new file geodatabase containing new mosaic datasets and feature classes.  We added the provided pre and post raster images.  I ran into some problems getting these images to display, but it finally worked after adjusting my scale and readding the raster images.  Using Effects such as the Swipe and Flicker tools we could compare and contrast the pre and post imagery.  

We learned how to create attribute domains using the newly created geodatabase's domain tab.  We then created a new point feature class for structural damage.  Using create features I created a point feature in the PreStorm image for each parcel within the study area.  After creating each point I turned on the PostStorm image and used the Swipe effect to look at differences between the images.   This enabled me to set the attribute values for the new attribute fields we created in the domain.  Working in a 1:400 scale seemed to allow me some detail to make my best judgement on attribute field values.  Determining the extent of wind damage was very difficult.  From the images, it appeared that most damage was the result of flooding.  The Post Storm imagery was very dark, appearing as if there was a lot of cloud cover that day.  With shadows in the image it was difficult to determine distinct differences between the images.  In real life I suppose you would have access to property appraiser/GIS data that would better describe the parcels as to whether the structure types were industrial, government, or residential.  Also, determining if a structure was inundated was difficult.  Was the building inundated or just the property?  Hard to tell from the aerial viewpoint if homes were raised up on stilts, pilings or blocks or on slabs.

Structural Damage Points in Hurricane Sandy Damage Assessment

Once I had my point features created it was time to examine patterns.  I used the multi-ring buffer tool to create the three buffer rings around the coastline polyline (100m, 200m, 300m).  Then I performed a spatial join between the Structure Damage points feature layer and the Multi-ring buffer.  I opened the attribute table of the join output and used Select By Attributes to perform the required SQL queries to complete the table below.

Structural Damage Category   Count of structures within distance categories from the coastline

                                                            0-100m          100-200m     200-300m___

No Damage                                      0                      0                      1

Affected                                           0                      1                      15

Minor Damage                                 0                      3                      7

Major Damage                                 0                      27                   21

Destroyed                                        12                     9                      2__________

Total                                                 12                   40                    46__________

Parcels that were closest to the coast received the most damage.  All of the structures on parcels within 100m of coastline were “destroyed” in my assessment.  Structures in the 200m buffer parcels were either destroyed or had major damage more than structures in the 300m buffer.

We performed attribute transfer mapping to assign parcel data to the structure feature points and then learned how to display labels showing some of the parcel attribute fields.

This final lab assignment was very long and covered many new tools in ArcGIS.  Each lab always reminds me of the power and knowledge that GIS can provide.