Threats

The hazard source data utilized in this assessment is available in a variety of different geospatial formats, including GIS Vector (points, lines, and polygons) types and GIS Raster (grid) data types. Assessing hazard threats using these native GIS data types, without first standardizing the data to a common spatial scale and reference would result in a set of outputs with very low utility to planners and decision makers. Overcoming the complexities inherent in this massive quantity of input and analytic data requires several steps be taken in order for results to be locally relevant and understandable to the general public.  First each dataset was converted to a common geography (hex grid) with an appropriate scale to assess each hazard at a level suitable to meet most requirements from state and federal entities, including HUD CDBG-DR “Description of the impacts geographically by type at the lowest level practicable (e.g., county level or lower if available, and neighborhood or census tract level for cities).”[1] And FEMA Hazard Mitigation risk assessments.[2]

A 0.25-square-mile hexagonal grid is used in this assessment because it provides the best coverage for small spatial areas while providing an ability to visualize spatial differences across the R2C AOI. Summarizing underlying spatial data to the 0.25-square-mile grid cell provides a grid-specific set of information that is fine enough to see patterns at a sub-county level and coarse enough to study each hazard threat across the entire R2C AOI.

Hexagonal (hex) grids represent a simplified method to display complex geospatial information[3] in an approachable way that also allows for aggregation of the data.[4] Using regular spatial bins (hexagons) serves three (3) primary goals. First, visual binning with hex grids simplifies data sets and aids in visual communication of complex data. If done correctly, visual binning can enable readers to make reasonable count or density estimates that would otherwise be impossible because of the complexity of underlying data. Second, spatial binning shows a smooth surface of aggregated values across larger areas. Finally, a standardized regular gridded framework, such as the hexagonal grids used here, enables analysis and evaluation within and between datasets that would normally be difficult (or impossible) to visually, statistically, or spatially compare.  

Step 1: Click on the filter icon (the funnel) and 

• Turn the tool on using the toggle in the top right 

• Select your (County/City) Area of Interest (AOI).  This will automatically zoom to your area of interest and show only hex grids intersecting your AOI.

Step 2: Apply additional filters for each hazard threat to further refine your AOI

Step 3: Click on the summarize button (calculator) icon to see a count of population and housing for your filtered selection.

Step 1: Select the layer icon from the top right corner

Step 2: Turn on/off your desired layers.