Composite Fingerprint Analysis of Sediment Sources in a Watershed Disturbed by Road Construction in Southeastern Tibet

Abstract

Construction activities such as road projects modify original land uses and intensify soil erosion. Understanding the sediment contributed by these projects and its spatial variation throughout a watershed is critical in terms of guiding conservation. Based on field sampling in a road construction-disturbed watershed in southeastern Tibet, a composite fingerprint analysis was conducted to explore the contributions of different sources to the deposited sediment. The results showed that 10 factors, including Al2O3, TFe2O3, Sn, total phosphorous (TP), Cr, Na2O, Mn, W, SiO2, and Sr, formed an optimum composite fingerprint combination. The multivariate mixed model revealed that the average contribution percentage rates of sediment deposited along the main channel were as follows: bank material (52.52%) > roads (33.02%) > forest and grassland (14.46%). The contribution percentage of road-related sediment fluctuated from the beginning point along the channel and was significantly correlated with factors such as the flow length to the channel (R = −0.6), road segment slope (R = 0.66), and ratio of the road length to the channel length (R = 0.65). The flow length to the channel was the most important factor affecting the road sediment contribution and a decreasing logarithmic function was established to describe the effect. These results have clarified how road construction spatially affects sediment at the watershed scale. They can therefore offer guidance for evaluating the environmental impact of human activities and supporting efforts in watershed soil and water conservation.