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. Most streams studied within Clear Creek County did not exceed their banks at the 100-year flood flow. These streams were not further analyzed for floodway considerations as the natural banks of the stream serve both as a boundary of the 100-year flood and the floodway limit. Only the confluence of Clear Creek and 'the West Fork of Clear Creek were analyzed for a floodway. Floodways were not determined for bridge cross sectIons and, there- fore, were not listed in Table I. The concept of a floodway and the encroachment upon a flood plain are not appl icable to roads and bridge crossings of a stream. Those lands dedicated to roads and bridges cannot be encroached upon as other lands in the flood plain and were, therefore, excluded from the floodway analysis. 5.0 INSURANCE APPLICATION In order to establ ish actuarial insurance rates, FIA has developed a process to transform the data from the engineering study into flood insurance criteria. This process includes the determInation of reaches, Flood Hazard Factors, and flood insurance zone designations for each flooding source affecting Clear Creek County. 5.1 Reach Determination Reaches are defined as lengths of watercourses havIng relatively the same flood hazard, based on the average weighted difference in water surface elevations between the 10- and 100-year floods. This diffenence did not have a variation greater than that indi- cated in the fol lowing table for more than 20 per cent of the reach: Average Difference Between 10- and 100-year Floods Variation Less than two (2) feet 0.5 foot Nine reaches meeting the above criteria were required for the flooding sources of Clear Creek County. These included two on Clear Creek, two on the West Fork of Clear Creek', and one each on Fal I River, Mi I I Creek, Chicago Creek, Beaver Brook, and Quay I e Creek. . 20