GEOGRAPHICAL RESEARCH ›› 1988, Vol. 7 ›› Issue (3): 58-66.doi: 10.11821/yj1988030008

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Shen Chenglie   

  1. Hangzhou University
  • Received:1986-12-08 Revised:1987-03-10 Online:1988-09-15 Published:1988-09-15

Abstract: The Yongjiang River is a micro-tidal alluvia] stream, but its upstream tridutaries mainly run through mountainous and hilly regions. The configuration and size of this river are relatively stable for a long tirne. A tidal barrier was built on the Yongjiang River, in 1959. As a result, the sedimentation was so serious that up to 1973, 3108×1104m3 of sediment had been accumulated in the Yongjiang river bed.In this paper, the basic characteristics of hydrodynamic action, sediment transportation and alluvial processes of the Yongjiang River have been dis-cussed. Based on the above analysis, a preliminary approach to the principles and measures of the regulation for the Yongjiang channel is made. The contents of this paper may be summarized as follows;In view of the small tidal range, larger variability of runoff and the ratio between the average flood flow and annual mean runoff volumes that is more than 12, the Yongjiang River, therefore, should be considered as a mountainous micro-tidal river. The tidal action is the main dynamics to fluvial processes. The boundary and bed of the Yongjiang River is composed of fine sediment which mainly derived from sea area.The fine materials are transported as suspended load.The general trend of sediment transportation and sedimentation may he described as follows; During flood seasons, owing to the effects of the ebb currents strengthened by the runoff, the sediment is carried and then silted downstream from the upstream reacn. on the contrary, the sediment is carried and then silted upstream from the downstream reach and out of the river mouth in non-flood seasons.The Yougjiang River is a meandering stream. The serious siltation of it should be attributed to the tremendous decrease of tidal discharge. After the construction of the tidal barrier and the training dikes, the processes of river bed are governed by the laws of siltation in the channel below the barrage, and in the curved mouth reach bifurcated channels has been cut.By dint of the above discussion, the principles of the regulation for the Yongjiang channel should be.1. Multi-purpose utilization of water resources.2. Keeping up pattern of meandering stream.3. Unchanged tidal inflow of the estuary.4. Combining regulation with dredging.5. Regulated elevation of middle tidal stage.In order to reduce the siltation, the following measures of regulation should be adopted.1. Operating the gate of the barrier and enlarging tidal prism.2. Enclosing and fixing tidal beaches.3. Extending the training dike and narrowing the river width.

Key words: Yongjiang River, Fluvial processes, Channel regulation