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The study relates to orographic effects caused by certain topographic features that appear to act as barriers to severe storms along the Front Range in Colorado. One example is Genesee Mountain, which appears to create an orographic effect, causing severe floods on Mount Vernon and Bear Creeks but virtually protecting the Clear Creek basin. Another example is the Rampart Range, which appears to protect the South Platte River tributaries to the west from severe storms. The questions to be answered are: (1) Can flash flood hotspots be identified, and (2) can a meaningful relationship be derived between elevation and frequency of severe thunderstorms? PROJECT DATA NETWORK An urgent need exists for hydrologic This project will provide the required data stations, rain gages, and crest-stage gages at data in foothill areas of Colorado. through establishment of gaging key locations. Several basins in which gaging stations, rain gages, and peak-flow crest- stage gages could be installed are listed in table 6 and are shown on plate 1. This list will be modified after completion of the network design and review by participating agencies. The project stations will be operated from April 15 to October 15 during each year. Gag i ng Stat ions A network of flood-hydrograph gaging stations will be designed during the research phase of the project, based on identified areas of data deficiency. In addition to number and location of required stations, the network design will also provide a probable length-of-data-collection period, which is presently estimated as a minimum of 15 years. Precipitation Gages As determined in the research phase of the study, each gaging station in the network will be equipped with a recording rain gage to provide concurrent records of streamflow and rainfall. Depending on the size of the basin, one or more additional rain gage will be located upstream in each project basin. Where appropriate, two or three project basins will be selected in the same general vi c in i ty to take advantage of a "group i ng effect" on the des i gn of the 'ra in-gage network. Crest-Stage Gages About 20 crest-stage gages were established during the 1978 water year (table 7 and pl. 1). Many of the crest-stage gages are located at discontinued gaging stations and are identified by a footnote in table 2. The crest-stage gages will provide data for extending the annual flood arrays at the previously gaged sites, with consequent improvements in flood-frequency estimates for the gaged basins. Depending on the outcome of the network design, some of the crest- stage gages may later be converted to flood-hydrograph gaging stations. 21