Research On Calculation Methods Of The Designed Navigable Stage And Water Stage Forecasting In Tidal Rivers

Since tidal rivers are influenced both by the runoff from inland rivers and by the tide from oceans, the variation rule of water stage and water discharge in tidal rivers is hard to grasp and it is also difficult to judge tidal river's attributes. In order to solve all above problems, theories on determination method for designed water stage of waterway engineering and technologies on tidal level forecasting in tidal rivers are studied in this dissertation. The main contents are as following:(1)The problem of judging the tidal rivers' characteristics is solved. The way by comparing "annual fluctuation of monthly mean level" AH which represents the runoff dynamic factors and "average annual tidal range" 8 which represents the ocean dynamic factors is put forward to judge tidal rivers' attribute. And it is improved and perfected by pointing out that the period we chose to compute AH and 8 should be different according to different situation.(2)The gist for choosing reasonable calculation methods for designed navigable stage is put forward. And with the case study of the lower tidal reaches of the Yangtze River, there come to a conclusion that Nanjing and Jiangyin are the two important dividing points in method choosing. And as far as the lower tidal reaches of Xijiang River is concerned, there come to some similar conclusions.(3) The cryptic period of the hydrologic time series of tidal reaches of the Yangtze River and Xijiang River are analyzed with the applying of spectral analysis and the result is reasonable. Furthmore the problem of data age which involved in calculating designed water stage is studied. And results show that the data age of the tidal reach is highly related to the distance from the tidal reach to the estuary.(4) Combined with analyzing the dynamic characteristics of non-stable hydrologic time sequences of tidal rivers, The ARIMA model and TAR model based on genetic algorithm are both excerpted into the prediction field of the tidal rivers successfully.(5) Based on the try of ARIMA and genetic TAR model in the tidal rivers, the ARIMAand TAR tidal level forecasting model of Baimao sand shoal are set up. The relationship between the forecasting accuracy and forecasting time step of the two kinds of model is also analyzed. And guided suggestions for forecasting model choosing are put forward.