感潮河网地区水系结构特征及城市化响应

根据20世纪80年代初以及90年代末上海水资源普查的数据,尝试以水利片作为河网地区流域水系结构的基本单元, 类似Strahler水系分级,采用上海水资源管理信息系统中的河道分级体系作为水系分级方案,探讨了感潮河网地区的水系结构特征及城市化响应。研究表明:(1) 非高度城市化地区河网水系总体上具有Horton表现,反映在非高度城市化地区不同水利片的河道数目及河道平均长度随河道级别呈几何级数变化,不同等级水系的发育具有自相似特征。(2) 城市化是改变感潮河网地区水系结构的重要因素,在高度城市化的城区水利片,不同等级河网水系发育的自相似性特征已受到破坏,其影响集中表现为对河网水系分枝比和水面率的削弱,即高度城市化地区河网水系结构趋于简单,非主干河道减少,河网水面率与城市化水平成反比,反映出城市化过程中未能充分与河网结构保护相协调。(3) 河网水系的结构与功能参数之间具有显著的相关水平,说明河网地区水系形态结构与功能密切相关。由于城市化进程表现为对水面率以及分枝比的削弱,指示水面率和分枝比等指标具有表征城市化对水系结构影响的意义,在河网水系保护和结构恢复过程中应高度重视水面率、分枝比以及河网结构自然度等指标。

Stream Structure Characteristics and Its Urbanization Responses to Tidal River System

Based on the data from Shanghai water resources survey separately conducted at the beginning of the 1980s and the end of the 1990s, taking water conservation 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 length of stream decrease in geometric series with the raising of stream order. Self-similarity of stream structure 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 task 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.