Do Debris Flows Pose a Hazard to Mountain-Front Property in Metropolitan Phoenix, Arizona?

Remnants of old debris flows occur on mountains that have been surrounded by growing suburbs of metropolitan Phoenix, Arizona, including on steep slopes above large single-family dwellings. Varnish microlamination and lead-profile dating techniques measured ages of 34 debris-flow levees in nine randomly selected catchments above home sites. Four catchments experienced debris flows in the last century, and four others had events in the last 350 years. Debris flows likely pose a modern hazard in Phoenix and perhaps other growing cities in the desert Southwest.