Applications in GIS - M5 Damage Assessment

 One of the most important steps in natural disaster response is the damage assessment; this analysis allows responders to scale the resources needed to assist and is the first step in getting a return from insurance and rebuilding aid allocated. 

The track of hurricane Sandy as it approached New Jersey, the icon color signifies storm intensity with red being Category 2 and green being Post-Tropical

When Hurricane Sandy hit the east coast of the US in October 2012, it came with high winds and a 9-foot storm surge that was augmented with waves and high tide in coastal areas. The assessment that followed was completed by FEMA contracting agencies, USGS, NOAA, and third parties. In this lab, we simulated a scenario, acting as one of those analysts to determine structural damage in the wake of hurricane Sandy storm surge. 

Mosaic files with imagery showing the New Jersey coast both before and after the storm

After creating hurricane track maps for context and developing a civilian self-reporting damage assessment in Survey 123, I loaded pre and post storm rasters into ArcPro as mosaic datasets, and used Swipe and Flicker mode to toggle between them. 

For the analysis, it was important to have constrained values - this means there were a limited number of acceptable values in the damage assessment, and helps standardize the way the damage is classified. To do this, I created the four domains Inundation, Structure Damage, Wind Damage, and Structure Type. The two damage domains were floats and had codes of 0 = No damage, 1 = Affected, 2 = Minor Damage, 3 = Major Damage, 4 = Destroyed. Inundation was a binary 0  = No, 1 = yes option, and Structure Type included the four values Residential, Government, Industrial, and Unknown. 

With these Attribute Domains created, I added a feature class to the Map with the same Damage, Inundation, and Structure Type fields. Once the layer was added, I was able to set the domains as the constrained attribute domains I had created in the Data Design dialogue. This successfully created a point feature class where the attributes could be selected from among the damage classes I created. 

The constrained fields that allow limited selection of attributes during structural assessment

At this point, by zooming into the mosaic imagery and examining property parcels, I used the Create Feature ability to add points to each structure; selecting as they were added whether that structure appeared to have structural damage, wind damage, or inundation, and classifying the structure type as the point was placed. This analysis was somewhat challenging; determining whether a building suffered minor or major damage based only on aerial imagery felt like a very subjective analysis. Additional data like vegetation surveys and elevation overlay would have helped make this more comprehensive.

Results of the damage assessment, with symbology indicating the degree of damage.

With a full set of categorized points providing structural damage assessment, I then added a polyline feature class and delineated the coastline. This allowed further analysis with the Buffer tool for how far different impacted structures were from the coastline. 

Overall, structures closer to the coast were more likely to be destroyed or have major damage, while structures further from the coast had a greater diversity of storm impacts.