Profile distribution of particle size of sediment at a check dam in small watershed in the Karst hilly region
[Background]The sediments is an important medium for retrieval of soil erosion characteristics,which indicates important information about the environmental process relation to soil erosion and deposition.[Methods]To investigate the characteristics and sources of sediment deposition in small watersheds of karst regions,the distribution characteristics of sediment particle profiles in small watersheds were analyzed and using field sediment stratification and sampling,indoor testing,and mathematical statistics.[Results]1)The particle size composition of sediment in a check dam is mainly composed of clay and medium silt particles,which account for 68.64％of the total proportion on average and their coefficient of variation is the smallest.The order of other particle sizes according to the average proportion of the total proportion is silt(13.69％),very fine sand(9.21％),fine silt(5.59％)fine sand(2.02％),coarse sand(0.82％)and large sand(0.05％);2)The sediment particle size profile of check dam siltation can be divided into three levels:＞0-30 cm with relatively uniform sediment particle size dominated by particles finer than fine silt,indicating land use transformation within the small watersheds;＞30-60 cm with better sediment particle gradation where all types of particle sizes basically distributed including a small amount of coarse sand and very coarse sand;＞60-85 cm with more uniformly distrbuted sediment partical size type compared with the previous layer,showing an increased proportion of coarse sand and large sand,which indicates the existence of rainstorm events in the control watersheds.3)At the depth of 60 cm,the characteristic particle size parameters and fractal dimension values of check dam silt reaches their maximum values,which is the turning point of the profile.indicating that the hydrodynamic conditions in the control watersheds are changed.The distribution characteristics of sediment particles in a check dam are closely related to land use control and water-sediment transport in small watersheds.[Conclusions]The distribution and variation of sediment particle sizes at different levels can provide insights into changes in land use within the watershed,the intensity of rainfall events,and alterations in hydrodynamic conditions.
万方数据
维普
