Recent debris flow studies in Colorado indicate that the state is most susceptible to debris flows that initiate from surface-water runoff that erodes and entrains hillslope and channel sediment. These runoff-initiated debris flows grow in size by entraining sediment along travel paths, thereby increasing their destructive potential. Yet, the mechanics of initiation, erosion, and entrainment processes for runoff-initiated debris flows are poorly understood. The steep, bedrock-dominated flanks of the formerly glaciated Chalk Creek Valley near Nathrop, Colorado, generate an average of two runoff-initiated debris flows per year, making the valley an ideal natural laboratory for debris-flow research. This two-day field trip to the Chalk Creek Valley will examine debris-flow initiation areas, transport zones, deposits, and the impact of large pulses of debris-flow sediment on the morphology of Chalk Creek. On the first day, participants will hike into a particularly active basin at Chalk Cliffs where debris flows are being monitored by the U.S. Geological Survey, the University of Colorado, and East Carolina University. The second day will focus on debris-flow deposits in Chalk Creek and on recent debris flows in and near the community of Alpine in the central part of the valley.