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The hydrology model in the basin is the major approach for analyzing the changes of water and sand, and assessing the benefits of water-soil conservation. Over the years, domestic and foreign research institutions and scholars established runoff and sediment yielding models based on the period of day. In this paper, the model of rainfall-runoff and rainfall-sediment of flood event in Gushanchuan watershed is established, and the impacts of climate change and human activity on runoff and sediment transport of flood event after 1979 are analyzed. 1 Selection of flood and precipitation Gushanchuan, the first-order tributary of the Yellow River, covers 1,272 km, locates in the overloaded and coarse sediment region, and 99.7% of the watershed exists in the centralized source area of coarse sediment. The watershed is the frequent occurrence region of high sediment flood. There are observed data from 1954 to 2010 in Gaoshiya, the control hydrology station of Gushanchuan. The flood peak over than average annual maximum discharge of 1350m/s is selected. The annual maximal flood discharge is chose in dry water year, if this value is lower than 1350m/s, and the occurrence of each choosing flood should avoid yearly peach flood. Only four rainfall stations exist in Gushanchuan watershed, and the building year is 1966, 1960, 1966 and 1953 respectively, thus the fifty one floods during 1967 to 2010 are chose. According to flood peak time and travel time, indicators of the flood and relevant precipitation are calculated. 2 Analysis of the turning point of water and sand The variation of runoff and sediment transport of flood event in Gushanchuan is analyzed by method of orderly clustering and MWP test. Thereby, the initial turning point from which human activity has notable impacts to hydrological series is ascertained. 2.1 Method of orderly clustering The orderly clustering method is used to estimate possible prominent turning point of hydrology series based on the time series [1]. Supposing the possible turning point of flood hydrology series is variableτ , the deviation square sum before and after turning point and the total is the following |
