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| Characteristics of typical rainstorm,flood and sediment yield in Luoyugou Watershed |
| Wang Ruifang<sup>1</sup>,Qin Baishun<sup>2</sup>,Huang Chengzhi<sup>1</sup>,Zhang Hulin<sup>1</sup>, Chang Dandong<sup>2</sup>,Dong Yuting<sup>1</sup>,Zhao Liyi<sup>1</sup> |
| 1.The Tianshui Experimental station on Soil and Water Conservation of Yellow River Conservancy Committee,741000,Tianshui,Gansu;2.Monitor Center of Soil and Water Conservation,Ministry of Water Resources,100053,Beijing: China |
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Abstract Based on the observed hydrology and sediment data and the flood investigation data in Luoyugou Watershed,the storm-flood-sediment characteristics of several typical torrential rainstorms causing extremely erosion were comprehensively analyzed.The results show that the deviation coefficient values of the area rainfall of the typical torrential rainstorms is 0.15-0.74,and the coefficient of nonuniformity is 0.37-0.90,and the ratio coefficient values of the extreme rainfall is 1.3-188.8.The maximum 10 min,30 min and,60 min precipitation in the heavy rain center area accounted for 19%-29%,35%-73%,and 60%-100% of the total rainfall;The flood volume of single storm accounted for more than 30% of the annual runoff,the runoff coefficient is 0.20-0.49,the modulus of maximum flood discharge is 4.07-9.34 m<sup>3</sup>/(s·km<sup>2</sup>),the total duration of flood is 6-96 h,the duration of rise is 15-80 min,the sediment discharge of single flood accounted for 60% of the annual sediment discharge,the sediment transport modulus of single flood is 7.1-14.0 thousands m<sup>3</sup>/km<sup>2</sup>,the maximum sediment concentration reache 774 kg/m<sup>3</sup>,the sediment peak is often 10-20 min ahead of the flood peak.The regression of the sediment hydrograph obviously lag behind in the flood hydrograph,the runoff with maximum sediment concentration is 40%-60% less than the maximum runoff.According to the contrast analysis,the difference of the storm-flood-sediment characteristics is mainly controlled by the temporal and spatial distribution characteristic of the torrential rain and the underlying surfaces conditions,and the effect of flood retention and sediment reduction of the soil and water conservation measures is obvious.
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Received: 27 August 2007
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