Formation and Development of the Potholes Formed in a Gorge River in Guangdong
广东大峡谷河床壶穴形态的形成与发育

Pothole geometries were measured in a reach of Dabu river bed at the head of a gorge that more than 200 m deeply incised 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 the field study were interpreted using standard statistical methodologies.The statistical analysis combining with related field observations revealed the origins of river potholes and the processes of pothole formation and development.The study shown that the formation and development of a river pothole were only related to the localized conditions,such as geology,geomorphology and water fluid styles at a spot where the pothole occurred;the weaknesses,which were usually intersected fractures,typically interconnected vertical joints,or triangular pits generated by hitting of rock fragments during floods,initiated pothole development on a river bed at this site;the geometrical dimensions of the potholes were controlled by the features of the tectonic joints developed in river bed rock;the radius and the depth of potholes were strongly(log)positive correlated;the shape of a pothole and the style of stream flows forming the pothole were not always the same in the processes of pothole growth;as an important role for channel incision,a pothole could create quickly in a gorge river undergoing powerful vertical erosion,but did not have enough time to fully develop and could not be maintained for a long time as well.