坡长对离石黄土坡面径流含沙量影响的模拟降雨研究

Impact of Slope Length on Sediment Concentration in Runoff under Simulated Rainfall in Lishi Loess Region

采用室内人工模拟降雨试验方法,探讨了离石黄土陡坡面降雨条件下坡长对径流含沙量的影响,并初步分析得出不同雨强范围内布设水土保持措施的临界坡长.结果表明,径流含沙量随坡长的延长呈波动变化趋势,且随雨强增大,含沙量达到峰值的临界坡长有所减小（雨强≤60mm/h时临界坡长为4m,雨强〉60mm/h时为3m）;坡长每延长相同长度,含沙量增量不相等且无明显变化规律;坡长1~5m时含沙量随雨强的增大整体呈增加趋势,但在60~80mm/h雨强时增幅最小,坡长2m和4m时增量甚至为负值,建议雨强大于60mm/h时需重点监测,以减少坡面水土流失;雨强与含沙量呈正相关关系,其与径流含沙量的相关性较坡长大（偏相关系数分别为0.810、0.383）,坡长、雨强与含沙量的关系可用线性方程描述（R^2=0.68）.

Based on the laboratory simulated rainfall events,the impact of slope length on runoff sediment concentration in Lishi loess region was investigated,and the critical slope length for soil and water conservation measures under different rainfall intensities were analyzed and obtained. Results indicate that runoff sediment concentration fluctuates with increasing slope length under the same rainfall intensity,and the critical slope length that sediment concentration reaches peak value decreases with increasing rainfall intensity（ the critical slope length is 4 m when the rainfall intensity≤60 mm/h,whereas it is 3 m when the rainfall intensity 〉 60 mm/h）.Increment of sediment concentration is not equal and there is no significant tendency with the same increase of slope length. The runoff sediment concentration increases with increasing rainfall intensity under 1 ~ 5 m slope length,and the minimum increment occurs under 60 ~80 mm/h rainfall intensity,even negative value at 2 m and 4 m slope length,therefore,it should be monitored intensively when rainfall intensity greater than 60 mm/h to decrease the soil and water loss in Lishi loess slope. There is a positive correlation between sediment concentration and rainfall intensity,moreover the impact of rainfall intensity on sediment concentration is greater than that of slope length（ partial correlation coefficients are 0. 810 and 0. 383,respectively）,and the relationship between sediment concentration and slope length and rainfall intensity can be described by linear equation（ Determination coefficient R^2= 0. 68）.