Abstract:

The goal of this study is to provide information on the process of pothole growth on a gorge streambed. Pothole geometries were measured in a reach of the Dabu river bed at the head of a gorge more than 200 m deeply incising into a 650–750 m high planation surface formed in the middle Miocene in northern Guangdong, China. Geometric and derivative data of the potholes obtained from fieldwork were interpreted using standard statistical methodologies. Our study shows that the formation and development of a stream pothole were only related to local conditions of a stream reach where the pothole occurs; the weaknesses, which are usually intersect fractures, typically interconnected vertical joints, or triangular pits generated by hitting of rock fragments during floods, initiate the pothole development on a streambed; the geometrical dimensions of the potholes are controlled by tectonic joints developed in bedrock of the stream reach; the radius and the depth of potholes are strongly (log) positive correlated; the pothole shapes and the flow patterns are inconstant during pothole growth; a pothole can be formed within a short period, but cannot be fully developed and maintained for a long time in a strong incision streambed. The finding in our study can improve the understanding of Quaternary environment in Guangdong.

Key words: Guangdong gorge, stream pothole, morphological feature