Abstract: In the aim of investigating the cumulative effect of debris flow on channel morphology, we analyzed the variations and influential factors of erosion and deposition in Jiangjia Gully according to sectional measurements from 1999 to 2014. Results revealed that the channel width increased continuously and the sectional height elevated or decreased depending on the erosion or deposition of channel. The channel width increased mainly from 1999 to 2009, and then remained stable after 2009 when erosion or deposition intensity decreased. Moreover, the curve of longitudinal profile of channel was concave, and the concavity index decreased gradually, fluctuating around 1.1 after 2009. The gradient of channel profile increased gradually, but the increment alleviated after 2009. Decreases in the sediment discharge, depth and velocity of debris flow, and debris flow afflux from tributary, as well as debris flow drainage project in the downstream were dominant factors influencing the channel morphology.

Key words: debris flow in Jiangjia Gully, inter-annual erosion and deposition, concavity index, channel gradient, erosion and deposition rate