Stream structure characteristics and its urbanization responses to tidal river system

Based on the data from Shanghai water resources survey separtated conducted at the begginning of the 1980s and the end of the 1990s, taking water conservayion zone, which is generally used to manage water resources and prevent serious flood, as the basic unit for stream structure analysis, this paper discussed the characteristics of stream structure and its growth laws under the situation of rapid urbanization in Shanghai. The research showed that (1) Horton law still plays an important role in some areas with relative lower urbanization level, and stream number and average lenght of stream decrease in geomatric series with the raising of stream order. Self-similarity of stream lies in different stream orders, (2) Urbanization is the dominant factor changing the structure of river system in urban area. In high-urbanized water conservancy zones, self-similarity properties of stream structure could not be observed. (3) There existed significant relationship between stream structure and its function. Because water area and stream ramification decreased obviously during the process of urbanization in Shanghai, it is an urgent tast to pay more attention to those indicators such as water area, stream ramification, river naturalness, and try best to maintain the reasonable values for these indicators.