Research On Calculation Method For Urban' Flood Prevention In Tidal River Exit Areas

Considering the question of flood prevention of cities in terms of the whole drainage basin, this thesis aimed at hydrological characteristic of tideway in debauchment area, has established the model for flood prevention and calculation of city which has complex hydrological conditions. The model is suit for underlying surfaces with many influencing factors and influenced by various water conservancy, such as, gates, pumps, weirs complex such as mountainous areas, plains, tides and kinds of water conservancy projects。The paper has studied the characteristic and reason for flood in cities in tidal river area, and then has summed up the assignments faced with and existent problems in the area. Considering the question of flood prevention of cities in terms of the characteristic of water system and difference drainage basin' surface, the area is divided in to coteau and campagna. Campagna is fractionized into the four area: surface, paddy field, dry land and town .Contra posing the four area, we adopt different calculative methods for produce and accordant junction. Then we took the calculative methods for invariable flow in river net to account flood factor in section. The text introduce the hydrological model -Xin'anjiang model which is suit for wet area to dry land , adopted 4-point Preissmann implicit scheme to explain Saint -Venant equations .Then ,we couple hydrological methods for produce and accordant junction and hydrodynamic methods in river net .The hydrology and waterpower model used for tidal river area, developed in this paper in of all-purpose function. The achievements of this paper not only have provided gist for the flood prevention plan of NingBo City, but also is applicable to other similar hydrological problems of cities in tidal river area.