Factors affecting slope runoff and sediment yield in northern Shaanxi Province based on path analysis

Based on data collected in 16 rainfall events with runoff and sediment yield on semiarid loess area in northern Shaanxi Province of northwestern China,we determined the main factors affecting runoff and sediment yield using path analysis. The runoff and sediment yield were set as dependent variables,while vegetation type,vegetation coverage,gradient,slope aspect,rainfall,rainfall duration,average rainfall intensity,I5,I10,I15,I30,soil bulk density and steady soil infiltration rate as independent variables. All the factors were processed by stepwise regression analysis. The following conclusions were reached: 1)Runoff was mainly affected by vegetation coverage, rainfall, rainfall duration, I30 and steady soil infiltration rate,while sediment yield was mainly influenced by runoff,vegetation coverage,gradient,rainfall,average rainfall intensity,I15 and soil bulk density. 2) Rainfall duration,rainfall and I30 were crucial factors affecting runoff; the factors affecting runoff based on the direct path coefficient were ranked in a descending order as rainfall duration I30 rainfall vegetation coverage steady soil infiltration rate; based on the indirect path coefficient,the order was rainfall rainfall duration steady soil infiltration rate I30 vegetation coverage; based on the coefficient of determination,the order was d rainfall·rainfall duration d rainfall duration·rainfall duration d I30·I30 d rainfall·rainfall duration d vegetation coverage·vegetation coverage. 3)Runoff,rainfall and I15 were critical factors for sediment yield; The descend order of factors affecting runoff based on the direct path coefficient were ranked in a descending order as I15 soil bulk density rainfall average rainfall intensity vegetation coverage gradient; based on the indirect path coefficient,the order was rainfall average rainfall intensity vegetation coverage I15 soil bulk density rainfall gradient; based on the coefficient of determination,the order was d runoff·runoffd runoff·rainfall d rainfall·I15 d I15·I15 d soil bulk density·soil bulk density d rainfall·rainfall.