Effects of landuse-landcover change on sediment production of runoff in typical watershed in the loess gully-hilly region of China

Landuse is found to play much more important role among the factors such as climate,soil properties,topographical feature,vegetation cover,human activities,etc.,which affecting soil erosion and sediment production.In order to understand the effects of landuse changes on sediment production and provide theoretical basis for landuse plan and management and ecological restoration,this study taking the controlled Qiaozidong Watershed and uncontrolled Qiaozixi Watershed in the third subregion of the Loess Plateau as examples,had analyzed the effects of landuse-landcover change(LUCC) on sediment discharge.The results showed that the impact of landuse-landcover on annual sediment yield was significant.The sediment discharging rate of controlled watershed had decreased by 44%, 75% and 86% respectively in wet,normal and dry years over the uncontrolled watershed.Comparing to the period of 1986-1994 for landuse in the controlled watershed,it was in period of 1995-2004 that sediment discharge reduced more.In addition,the impact of landuse-landcover on sediment discharge demonstrated seasonal fluctuation characteristics. The effects of sediment reduction in the controlled watershed displayed more significance than that in the uncontrolled one in May and September.To the controlled Qiaozidong Watershed,the reduction effect consisted with rainfall distribution.Finally,the flood sediment discharge had closely correlated with the rainfall amount,rainfall intensity in 60 min and the flood volume,and had greater impact on flood sediment discharge in the uncontrolled watershed than that in the controlled watershed.Rainstorm-runoff process and the rainstorm-sediment discharging process demonstrate that landcover has strong regulation and control function on flood process and sediment discharge process in rainstorm.For the Qiaozidong Watershed,in the same precipitation frequency distribution,the mean sediment concentration in the latter landuse period(1995-2004) was fewer than that in the former landuse period(1986-1994) under all recurrence periods.