Author(s): Null
Linked Author(s):
Keywords: Meandering rivers; Bend cutoffs; River management
Abstract: Natural rivers are dominated by meandering channel Pattern. The associated channel migration involves progressive changes of channel position overtime as well as abrupt and rapid changes. Due to the roughly- equilibrium sediment transport in nature, meandering river often shows the characteristics of “concave scouring and convex silting”. With the continuous development of the curve, the curvature of the river channel is further increased, which often leads to the occurrence of bend cutoff when encountering overbank Flood. Due to the suddenness and uncertainty of these changes, it is difficult to predict the specific time and process of such events. The Lower Jingjiang of the middle Yangtze River is a typical meandering river, with occurence of many natural bend cutoffs in history. In the 20th century, there were two demonstrable natural cutoffs: Chibakou cutoff occured in 1909 and Shatanzi cutoff occured in 1927. And two artificial bend cutoffs were implemented this time. The cutoffs shortened the length of the river, lowered the upstream flood level, and stabilized the river regime. And also, several negative effects such as damage to the flood control projects and loss of wetland resources are gradually emerging. In this paper, Shatanzi cutoff is studyed through detailed analysis of the measured data, with particular attention to factors that may trigger cutoff. it is concluded that the planform with large curvature is the basic condition for the natural cutoff, and that sufficient flood time and large water surface gradient are the burst hydraulic factors of natural cutoff. Based on the current river regime of the lower Jingjiang and the relationship between Jingjiang and Dongting Lake, it is estimated that when the inflow of the Lower Jingjiang exceeds 40000 m3/s for more than 3 days, with relatively small outflow of the Dongting Lake concurrently, there’s a strong possibility that natural cutoff occur at the Baxingzhou bend. This conclusion may provide reference for cascade reservoirs operation in the main stream of the Yangtze River and the Dongting Lake basin and comprehensive management of the Lower Jingjiang.
Year: 2024