Wittmann H-3 Area Two-Dimensional Alluvial Fan Floodplain Analysis

Maricopa County, AZ

PACE provided a hydraulic evaluation of the characteristics and overland flow necessary for developing a 2-D model to help identify drainage facilities and cost estimates for the H-3 Fan in the Wittmann Area Drainage Master Plan study area.  The scope of work involved collection of the necessary documents and available data to establish and revise the hydrology and perform flow 2-D analysis. PACE reviewed and collected existing hydrology, hydraulics, soil type and gradation data, land use and parcel maps, and culvert rating curves, using GIS-based techniques, when applicable. Field reconnaissance of the existing watershed conditions as well as ground photo survey of fan conditions within the study boundary where also analyzed.  PACE also performed GIS-based topography development and grind resolution determination.  A baseline FLO-2D hydraulic model was used to prepare floodplain models.  A sectional discharge analysis was used to estimate runoff hydrographs for model sections based on on-site property boundaries. PACE also determined the Bureau of Reclamation hazard zones for the 100-year, 24-hour and 100-year, 6-hour storm events.