Stream Structure Characteristics And Its Urbanization Response In Dense River Network Plain: A Case Study Of Shanghai,China

Rivers are invaluable natural heritage. River networks have their effects on river style, stream structure, flood-control capacity and water cycling process through the factors such as stream bifurcation, stream order, river density, river frequency, stream number and length. After water quality having been extremely improved in developed countries, people now have taken it as important target to restore rivers to their natural situation. River style and structure have now becoming the key contents for river management and river health assessment. River systems are one of the most deeply modified eco-systems in the world. Based on natural laws, river systems have their regular features formed in the evolution process. Under the human modification, part of the natural style and structure of river systems have been affected even been destroyed. This is one of the main courses that caused more and more serious flood and water environment pollution.Yangtze Delta is a plain with well-developed river networks. To keep the health of river networks and natural-like stream structure, that is the precondition for eco-city construction in such regions. However, urbanization changed the landuse. A large amount of branches were engineered out, the natural flood-control capacity of river systems were weakened, stream structure is becoming more and more simple and the diversity of natural river style is seldom observed in urbanized area. Since 1990s, cities in Yangtze delta had begun to replan and restore urban river systems. Therefore, studying the characteristics of river systems and its urbanization response in Ynagtze Delta, that is academic base for restoring and protecting river systems. The following questions have been faced and need to be answered for realizing health urbanization in river network regions, (a) How to define river basin and stream order? (b) The characteristics of stream structure situation and river systems development;(c) the correlation between stream structure and flood control capacity of a river system; (d) How to classify river systems? Are there any regulations that may guide the evolution of river systems?...