ALLUVIAL-FAN - PROPOSED NEW PROCESS-ORIENTED DEFINITIONS FOR ARID SOUTHWEST

The Flood Control District of Maricopa County, Arizona, recently compl eted a study whose purpose was to select and describe four alluvial fa ns for instrumentation and long-term monitoring. One primary result of this study was the development of new technical, process-oriented def initions to describe and differentiate among the types of alluvial fan s found in central Arizona. These alluvial fans, while exhibiting the generic, regulatory fan shape, are subject to different types of hydra ulic processes. Tables identifying the characteristics and hydraulic p rocesses on each type of landform found in the study area were also de veloped. These new definitions provide a framework for engineers and r egulators to discuss landforms with a common terminology that is tied to the relevant expected hydraulic processes.