Acta Geographica Sinica ›› 2017, Vol. 72 ›› Issue (7): 1195-1206.doi: 10.11821/dlxb201707006

• Orginal Article • Previous Articles     Next Articles

Planform characteristics and developing level of interchannel wetlands in a gravel-bed anastomosing river, Maqu Reach of the Upper Yellow River

Boyi LIU1,2, Suiji WANG1,2()   

  1. 1. Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China
    2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-01-03 Revised:2017-03-04 Online:2017-08-07 Published:2017-08-08
  • Supported by:
    National Natural Science Foundation of China, No.41571005, No.41271027

Abstract:

Interchannel wetlands as well as multiple channels are crucial geomorphologic units in an anastomosing river system. Planform characteristics and developing level of interchannel wetlands and multiple channels have effect on anastomosing rivers. To understand the role that interchannel wetlands play in the development of the anastomosing river, a study was carried out at the Maqu reach of the Yellow River, a gravel-bed anastomosing river characterized by highly developed interchannel wetlands and anabranches. Geomorphologic units in the study reach were extracted from high resolution satellite imagery in Google Earth, size distribution of interchannel wetlands and interchannel wetland clusters (special combination of interchannel wetlands and anabranches) were investigated, and geomorphologic parameters including ratio of interchannel wetland area to interchannel wetland cluster area (P), shoreline density (Dl) and node density (Dn) were used to examine planform characteristics of interchannel wetland clusters and the development level of multiple channels in the study reach. The results suggest that interchannel wetlands with small or medium size and interchannel wetland clusters with large or mega size are more common in the study reach. The area of interchannel wetland cluster (Su) is highly related to other geomorphologic parameters, P increases with the increase of Su, with 80% of P value being basically the upper limit, indicating that the development of interchannel wetlands and anabranches in an interchannel wetland cluster has entered a equilibrium stage. In contrast, Dl and Dn show a tendency to decrease with the increase of Su due to evolution processes diversity in interchannel wetland clusters with different sizes. There are three main reasons for the formation of interchannel wetland clusters: stream power diversity caused by the meadering principal channel; development of river corridor due to the weakening of geologic structure control; and high stability of interchannel wetlands due to conservation by shoreline vegetation.

Key words: channel planform, gravel-bed anastomosing river, interchannel wetland, geomorphologic parameter, Yellow River