Feature A selection of CAD layers provided groundwork for later GIS development. Elevation data had to be incorporated into the spatial framework. The scatter-plot matrix, showing the highlighted GPS points, was created during the initial analysis of coordinates and elevations. address unforeseen complications in the future, the village turned to GIS so many aspects of hydrology could be combined. With GIS, floodplains could be overlaid to help analyze and predict events rather than simply present data. The village already had most of the information needed to predict both flood levels and the specific areas that would likely be affected by any one flood. However, while initially the data was available to decision makers, this data was separated into many files stored on many computer systems and could not be easily gathered or studied. The maps, AutoCAD files, miscellaneous spatial information, written memoranda, and other files needed to be combined with www.esri.com data collected from the area and presented in a way that would allow the village government to better analyze and address not just flooding problems but also other hydrology issues. The existing information was sufficient to predict possible floods and their locations, but due to the problem with the storm water system, the extent could not always be predicted. The additional data on, for example, which houses needed to be removed from the sewer system, once collected and combined with the existing information, would not only allow the extent of possible floods to be better predicted but also assist in dealing with certain issues with the storm water system that was being modified. It was determined that preexisting information would be merged in ArcMap. GPS data would provide more accurate elevations, digital images around the village would help better visualize and predict flood levels, and aerial and topographical maps would be overlaid to provide context for the entire village. The aerial and topographical maps allowed an additional analysis of the watershed for areas outside the floodplain to determine their possible effects on the village's storm and sewer water systems. A field crew used GPS equipment to collect horizontal and vertical data around the floodplain. The project was concerned with a specific aspect of hydrology. Within this limited area, a more accurate topographical representation of the floodplain and the surrounding areas was required in part to correctly identify which homes and how much water shunted into the river and sewer system would be captured by the storm water system. GPS was used to acquire highly precise horizontal and, even more importantly, vertical benchmarks so the many other kinds of information could be accurately incorporated. Of the information to be included, a correctly projected and transformed aerial raster set for the entire village was the most challenging to obtain. With this accomplished, the rest of the project could correlate this information with the topographical data relating to the river and the storm water systems throughout the village. Both systems play a large role in the dynamics of the watershed and risk of flooding. With a basemap and the rest of the information for the entire village in place, proper analysis could be performed at a much higher level of specificity, and these analyses could be more easily performed for future hydrological projects. Through careful spatial analysis using ArcGIS, small and rural local governments can make more informed decisions regarding their existing infrastructure. Many of these communities already have the necessary data at their disposal but lack an effective way to leverage this disparate data. GIS can give these governments a tool to better analyze their existing knowledge base. For more information, visit the ArcGIS Resource Center for Water Utilities. About the Author Craig A. Ries is a GIS technician with David Arthur Consultants, Inc., and can be reached at dac@cass.net. ArcUser Winter 2010 29