Vote — approved

Steve Gallardo	yes
Jack Sellers	yes
Bill Gates	yes
Clint Hickman	yes
Steve Chucri	yes

85.IGA WITH ADOT FOR DEVELOPING DEPTH-AREA REDUCTION FACTORS FOR ARIZONA Approve the Intergovernmental Agreement (IGA) between Arizona Department of Transportation (ADOT) and the Flood Control District of Maricopa County (District) for the development of updated depth-area reduction factors for Arizona. As part of the agreement the District will fund the costs of the study that benefit watersheds affecting Maricopa County and ADOT will fund the costs of the study that benefits watersheds that af

Item Text

85. IGA WITH ADOT FOR DEVELOPING DEPTH-AREA REDUCTION FACTORS FOR ARIZONA Approve the Intergovernmental Agreement (IGA) between Arizona Department of Transportation (ADOT) and the Flood Control District of Maricopa County (District) for the development of updated depth-area reduction factors for Arizona. As part of the agreement the District will fund the costs of the study that benefit watersheds affecting Maricopa County and ADOT will fund the costs of the study that benefits watersheds that affect Arizona, but outside Maricopa County watersheds. The District will fund $380,000 of the study and ADOT will fund $60,000. Engineers use rainfall depths developed by NOAA to complete studies that identify and evaluate flood hazards. These values are also used to design drainage facilities (culverts, basins, bridges, etc.). A depth-area reduction factor (DARF) is one of the factors used in the rainfall determination. The current Drainage Design Manual, Hydrology Volume includes reduction factors developed in 1974 for the 6-hr storm event and 1984 for the 24-hr storm event. Recent studies have been compared to gage data and other storm evidence, and have shown that updates are needed. Proper factors for determining rainfall are important to properly size drainage facilities. This Agenda Item impacts all Supervisor Districts. (C-69-21-087-X-00)

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