Most of central Arizona is covered with basin sediments composed largely of unconsolidated sands and gravels. These deposits are important to planners, engineers, and geologists as they are the reservoir for vast amounts of groundwater, the source of important industrial materials, and the physical matrix that supports roads and buildings for most of Arizona's inhabitants. In addition, the bedrock geology of this area is complex and interesting, and hosts potentially economic mineral resources. Expanding population and burgeoning development in the Greater Phoenix metropolitan area requires more information regarding its geological resources and the spatial distribution of geologic hazards such as flooding that are common to basin environments.