Modeling sediment transport in the pantano wash, Tucson

Hydrodynamic and sediment transport models are useful engineering tools for predicting flood flow. Many models such as HEC-RAS, HEC-6, IALLUVIAL, and GSTARS were developed for perennial rivers, and may not be suitable to ephemeral rivers in arid and semi-arid regions. This report outlines a study that examined the applicability of HEC-RAS 4.1 model in simulating flood flow and sediment transport in dryland streams in the state of Arizona. The objective is to determine if HEC-RAS model, especially the newly developed sediment transport model, is accurate in predicting erosion and sedimentations. The method of model verification and validation will guide other sediment modeling projects in other streams including the Salt River and the Verde River and their tributaries in Arizona, as well as the ephemeral rivers of Pima County. This study also examined various sediment transport formulas and recommended Yang's or Ackers-White's equations are the most appropriate formulas for sediment transport analysis in this region. Based on this study, we expect that the sediment transport analysis for dryland streams will be performed by using Yang's or Ackers-White's equations in HEC-RAS 4.1 model.