Feature The pie chart shows the percentage of the county’s 3,794 properties that were affected by the flood. The chart inset shows the percentage of residential properties under different floodwater levels. The photograph shows a section of Six Flags theme park that flooded. Hmin = 0 or H - Mmin if H > Mmin Hmean = 0 or H - Mmean if H > Mmean Hmax = 0 or H - Mmax if H > Mmax Where Hmin, Hmean, and Hmax are the minimum, mean, and maximum water heights and Mmin, Mmean, and Mmax are the minimum, mean, and maximum ground elevation values, respectively. The formulas above are used for calculating floodwater heights for each parcel. The parcel feature table was then joined with the ownership table to obtain the parcel class (e.g., commercial, residential, public www.esri.com property). ArcScene was used to generate a three-dimensional visualization of the flooded area. The field inspectors were provided with situs addresses along with the flood height information for the parcels. This information helped them easily identify and determine the extent of damage for each property. The county has since established a river model in HEC-RAS to help ensure future flood inundation boundaries can be obtained with better accuracy. [HEC-RAS, or the Hydrologic Engineering Center’s River Analysis System, is a software program developed by the U.S. Army Corps of Engineers for performing one-dimensional steady flow, unsteady flow, sediment transport/mobile bed computations, and water temperature modeling.] Information is the lifeline of any EOC, and GIS technology is a valuable tool when it comes to managing and analyzing data and ensuring its broad availability. Through the use of GIS, Cobb County was able to quickly determine the approximate extent of flooding; generate maps and reports that helped first responders, inspectors, and repair crews prioritize the areas to visit; and publish information to department managers and personnel via a Web mapping application. For more information, contact Tim Scharff, GISP, GIS Manager, at tim.scharff@ cobbcounty.org Seth Agyepong, GIS Supervisor, at seth. agyepong@cobbcounty.org Vinu Chandran, GIS Specialist, at vinu. chandran@cobbcounty.org ArcUser Spring 2010 29