THE RESEARCH
Methodology:
In order to asses the floodplain exposure, FEMA flood zone data was downloaded and symbolized by zone. Zones AE, AH, AO, and VE were merged to comprise the 100 year floodplain while the four zones plus zone X with a 0.2% annual chance of flooding comprised the 500 year floodplain. Data for 1.5 feet, 3 feet, and 4.5 feet of sea level rise were also downloaded from Norfolk Open GIS Data. Next, asset data was downloaded from several sources, including Norfolk Open GIS Data, Hampton Roads Geospatial Exchange Online, the City of Virginia Beach Open GIS Data, and the USDA. In the end, there were 38 different assets categorized into seven groups: Building & Housing, Community, Government & Planning, Health & Safety, Natural, Transportation, and Water & Waste. All floodplain, sea level rise, and asset data were added into ArcMap. Once all the data had been sourced, the following step was the spatial analysis. Using select by location and the geoprocessing clip tool, each asset was analyzed to calculate the amount that fell within the 100 and 500 year floodplains and each sea level boundary. The type of data dictated how the calculation was processed.; points and polygon building data were calculated by the count of each asset that fell within a boundary, while polygon land data was calculated in acres, and line data was calculated in miles. The exposure results were recorded in an excel spreadsheet where percentage calculations could be made. The calculated results were then graphed and mapped. Once the desktop analysis was complete, the ArcMap project was shared as a service to ArcGIS online where an interactive web application was created for public access.
The Results:
The spatial analysis results showed that in total, 30.74 square miles of land fall within the 100 year floodplain and 43.65 square miles fall within the 500 year floodplain. In addition, 4.06 square miles of land would be covered in water due to a 1.5ft increase in sea level, 6.96 square miles due to a 3ft increase in sea level, and 10.92 square miles due to a 4.5ft increase in sea level. Natural assets are most threatened with a total exposure percentage of 21.67% within the 4.5ft sea level boundary and 59.90% within the 100 year floodplain. This is followed by Government and Planning assets with a total exposure of 18.47%, Community assets with 15.27%, Transportation assets with 13.99%, Building and Housing assets with 13.30%, Health and Safety assets with 7.73%, and Water and Waste assets with 0%. Figures of these results can be found here.
The table containing all asset calculations can be seen below.