The Change Of The Mid-Downstream Bed-Downcutting In Xijiang River And The Improved Research Of Flood Forecasting

Since the nineties of the last century, a large amount of sand has been excavated from Xijiang river, especially the lower reach section of Zhujiang Delta. It makes the riverbed down-shears year by year, the slope of water surface increases and the surface profile becomes steeper, which leads that the flood forecasting schemes of Xijiang river will deviate from or deviate from seriously, for the stations of Wuzhou, Deqing, Gaoyao and Makou.The thesis analyzes something about the Xijiang river, such as the change of riverbed, the relation between the hydraulic key elements along the course and the surface profile, and the hydrology situation change of the section. It also discusses the influence to the flood forecast scheme because of the riverbed's declination. Combined with the current real-time flow forecasting and the correction method, this paper puts forward a plan to remedy the flood forecasting scheme, which is suitable to the Gaoyao station, then researches the improving application based on the plan. By the high precision flood forecast model, which is suitable to the Gaoyao hydrologic station, it is more propitious to the flood forecasting and prevention of the middle and lower reaches of Xijiang river. The main content of the research paper is:The paper is divided into nine chapters. Chapter one summarizes the development history of the flow forecasting and research contents of the thesis, and introduces the watershed and river system general situation of the Xijiang river; Chapter two introduces the detailed situation of the riverbed's declination; Chapter three analyzes the change of the hydrologic situation of the Xijiang river; Chapter four studies the influence to the flood forecasting because of the riverbed sink; Chapter five talks about the hydraulic factors which influence the flood forecasting; Chapter six expounds the real-time flow forecasting and the correction methods ; Chapter seven discusses the plan to amend the current forecast scheme, and puts forward the flood forecast model which is propitious to Gaoyao with a view to riverbed's declination factor etc. Chapter eight analyzes the improvement of the flood forecast scheme, and sets a model of corresponding water stage from Wuzhou to Gaoyao according to parameters such as the flood classifying of Beijiang and the synchronous water of Gaoyao, and sets the fluctuating water models of the upper and the lower reaches stations respectively; The final chapter provides the conclusion and suggestion.