Urban geomorphology of an arid city: Case study of Phoenix, Arizona

The urban metropolis of Phoenix, Arizona, USA rests on classic desert landforms, including extensive areas of pediments, alluvial fans, aeolian sand sheets, and former areas of desert pavement. The Phoenix area landforms exemplify classic desert geomorphic processes, such as rock varnish accretion, the rock decay processes of dirt cracking, desert pavement formation, rockfall, debris flows, high magnitude-low frequency flooding events, and pedimentation. Recent urban expansion has pushed housing up against the base of steep desert slopes capable of generating debris flows, rockfalls, and rockslides. Other geomorphic hazards experienced by urbanism in the desert include dust storms and flash flooding. The Phoenix metropolitan region offers an opportunity to explore the impact of the Anthropocene, the proposed new geological epoch defined by the human imprint, in a warm desert setting impacted by cattle crazing, wildfire that results from introduced grass species, and urbanization processes, such as road building and home construction.