Fractal characteristics of watercourse evolution of the Lower Jingjiang segment in middle Yangtze River

According to the fractal analysis of segments (covering 100 years) of the Lower Jingjiang in middle Yangtze River, the fractal characteristics was discusses in this paper. Our results showed that the parameter of dimensions, encompassing 1.078 to 1.230, are lower than those of Yellow River, Haihe River and Luanhe River and close to those of plain areas in lower Yellow River reaches and upper Yangtze River reaches, referring to the mature segment. Especially, the values are disproportional to other segments of this catchment, actually reflecting the control of its geological settings. The author interpreted this as the result of long-term slow subsidence of Jianghan-Dongting Lake plain. After the watercourse is cut off, the fractal value deceases evidently associated with the simplification of watercourse. The curve cut-off of segment is an abrupt event, only occurring when the dimension is between 1.19 and 1.23, thus can be regarded as an early warning parameter.