Anthony Phillips Department of Geography Virginia Tech In Cooperation with:

Identify, measure, and analyze areas in Pulaski County that are prone to flash flooding using GIS. Results will be compiled in digital form onto a DVD, as well as in paper form in an operational handbook. All data will be overlaid in Google Earth and accessible from workstations at the NWS.

#1 weather-related killer in the United States! Can occur nationwide, in any environment, but primarily affects these areas in Pulaski County: River flooding Small stream flooding Urban flooding Dry wash flooding

USGS road and stream shapefiles were imported into ArcGIS. Software was used to select points where roads and streams were within 25’ of each other. 651 points identified.

Following data collected at each road-stream intersect point: Road name Road type Stream name Stream flow (slow, normal, fast, none) Distance from road to stream Angle of depression Upstream picture Downstream picture

Distance from road to stream calculated from eye-level to stream edge. Standard 50’ measuring tape. From same location, angle of depression measured from eye-level to stream edge. Clinometer

θ° d FS= [d x SIN(θ°)] – 6’ 6’ FS Picture by Sarah Prescott

Of the 651 points initially plotted by ArcGIS, 319 were fully documented. The remaining 332 points were either on private roads or were not likely to have flash flooding.

Final data was imported into ArcGIS. Each measured point was color-coded to indicate the height of flood stage visually. Red: <1.5’ Orange: 1.5 – 3.0’ Yellow: 3.0 – 5.0’ Green: 5.0 – 8.0’ Turquoise: 8.0 – 12.0’ Blue: >12.0’

2007 aerial photography serves as the background for each map. Subbasin information and GIS polygons were provided by the NWS and are the same basins used in AWIPS and FFMP. Additionally, each map includes all roads and streams with their associated names, as well as an inset map of surrounding elevation.

The exact location and information for each measured point was imported into Google Earth. Additionally, each subwatershed basin was also imported. Points were color-coded based on the same symbology used in ArcGIS.

Conclusions are still being drawn at this time, but overall the project has been a complete success. Areas that are susceptible to flash flooding have been fully documented. All information has been mapped and imported into Google Earth. Information will be available to the NWS and County of Pulaski in the form of a handbook and/or DVD.