黄土高原小流域淤地坝泥沙粒度的剖面分布

2006年6月，按照泥沙旋回分层连续取样，分析了黄土高原丘陵沟壑区典型小流域1954年修建的淤地坝泥沙粒径的剖面分布特征.结果表明：该坝地泥沙旋回至少28个，旋回层的厚度范围在2～60 cm；沉积剖面土壤粒径以粉砂（0.05～0.002 mm）为主，占60%以上，其粒径集中分布于0.01～0.05 mm，粗泥沙（粒径>0.05 mm）含量约占23.09%；随淤积深度的增加，泥沙各粒径范围的变异程度增加，2 m土壤深处可作为研究区淤地坝粒径变异突变点的标识，粒径变异是河道比降和水沙动力条件共同作用的结果；研究区淤地坝泥沙沉积剖面存在72 cm厚的累积耕作层，累积耕作层的明确对于淤地坝泥沙侵蚀环境具有指示作用.

Profile distribution of sediment particle sizes at a check dam in a small watershed of Loess Plateau

Sediment gyration sampling was conducted in June 2006 to analyze the profile distribution of sediment particle sizes at a check-dam built in 1954 in a typical small watershed of hilly and gully Loess plateau.There were at least 28 layers of sediment gyration at the check-dam,with the layer depth varied from 2 cm to 60 cm.In the sediment profile,silt(0.05-0.002 mm)occupied＞60%,its particle size being mainly within the range of 0.01-0.05 mm,while coarse sand(＞0.05 mm)accounted for 23.09%.The variation degree of sediment particle sizes increased with increasing depth,and an abrupt change was observed at the depth 2 m.Both longitudinal gradient and hydrodynamic condition caused the variation of sediment particle sizes.There was an accumulated plough layer of 72 cm thickness in the profile,which had indicative role for the sediment erosion environment of check dam.