Return Value Estimation Of Sudden Siltation Volume For Silt-sand In Coastal Area Under Strong Winds

Sand on silt-sand beaches moves actively. The threshold velocity is small and the setting velocity is large, and rapid siltation often occures. Therefore, such beaches were regarded as the forbidden zones for constructing ports in the past time; little research was made in this type of beaches because of little understanding of its hydraulic characteristics. there are many silt-sand beaches in our country coastline. With the rapid development of the national economy, the sea ports and navigation channels are built or have been built,meanwhile serious siltation occurs in these nearshore areas. Especially under strong winds, severe sudden siltation occurs in its navigation channel, severely influences the normal constructions and operations, and results in enormous economic loss. Therefore researching siltation on the silt-sand beaches has high practical and economic value.Mechanisms of siltation in the outer channel are sediment surged up by wave and sediment transported by current, And are controlled by a wide range of conditions, such as:siltation environment, sediment characteristics, the type of sediment migration, ocean dynamicial force, channel scale, etc. For silt-sand beaches, the factors affecting siltation in the outer channel change great, and mechanisms affecting siltation are more complex, So far there is not more appropriate formula for calculating siltation of channel. On the base of'effective energy of wind', this paper estimates the return value of sudden siltation volumes for silt-sand beaches, which will provide some practical significance data for constructing silt-sand ports.The main of this paper is as follows:(1) Statistics analysis of the hydrological and meteorological data of the project location;(2) Use the concepts of'effective energy of wind', directly establish the relationship between wind data which observed easily and siltation volume of channel, give the empirical formula of siltation of channel, and contrast with the siltation data of actual observation to choose the suitable coefficients for the coast. According to the long-term wind data, calculate the siltation volumes of channel;(3) Use several common extreme value distributions, respectively use annual extreme value method, POT method and combined distribution to estimate the return values of siltation volumes, provide the technical parameters for siltation prevention of channel after selection;(4) Calculate and compare method of moments, probability weighted moments method, linear moments method, maximum likelihood method and least square method, and solve their numerical solutions.