FLOOD04808 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I - 9 - selected by the engineer and used as a basis for Mr. Mulvey's storm calculations. His reports, in Appendix A, go into detail of the meteorological events that lead up to the creation of a thunderstorm, Table 3 summarizes the design rainfall for the Blue River. Table 3 RAINFALL DATA, BLUE RIVER FLOODS Storm 10 year 25 year IRF SPF Design Rainfall 1. 8 inches 2.5 inches 2.8 inches 9.2 inches The storm condition with the greatest potential for producing maximum flooding along the Blue River occurs above the Goose Pasture Tarn and st~addles the Continental Divide. Mr. Mulvey describes each storm as being multi-cell with only a portion of the cell contributing runoff to the Blue River basin. The storm event had cells centered over Red Mountain and Borreas Pass ~1ountains. The areal extent of upper basin storms is described in the report by Mulvey. While Mr. Mulvey's reports define the most probable location and areal extent of the maximum potential storm for each frequency event in the basin, it is possible for flood producing storms of smaller magnitude to occur elsewhere. Runoff was determined from storm events occurring over major tributaries of the Blue River below the "Tarn". Table 4 sununarizes the design rainfall for the tributaries. Table 4 RAINFALL TRIBUTARY FLOODS Storm 10 year 25 year IRF SPF Design Rainfall 1. 5 inches 1.6 inches 2.0 inches 9.2 inches For the tributary basins the storm was assumed to be centered over and cover the entire individual tributary under investiga- tion. The rainfall has been reduced for areas less than 10 square miles. Each storm, including those centered over the tributaries, was assumed to be of 6 hour duration. ~ Leonard Rice Consulting Water Engineers, Inc.