泥石流泥沙输移比的概念与计算方法探讨

通过泥石流SDR,可将泥石流流域侵蚀产沙、泥沙输移及泥石流沟道和入汇处主河河床演化有机地联系起来,用于推求流域的土壤侵蚀量,泥石流沟道的冲刷与淤积状况,泥石流所输送的泥沙进入主河的数量,以及对下游河道演变、水库使用年限的影响程度等方面。但目前泥石流SDR的研究还没有开始,在分析泥石流输沙特征的基础上,将SDR引入泥石流输沙的研究中,并将泥石流SDR分解为反映泥石流沟输沙能力的沟道泥石流SDR和反映主河输移泥石流泥沙能力的汇口泥石流SDR两个环节。给出了根据定义使用实际的监测数据计算两类泥石流SDR的具体方法,并在蒋家沟中实施,计算出蒋家沟2007年的一场泥石流过程中沟道SDR为0.14,入汇主河后的悬移质汇口泥石流SDR为0.36。泥石流SDR的模型计算法方面也根据定性分析列出了可能的影响因子,在总结河流SDR的研究成果和分析泥石流输沙特性的基础上进行了模型建立方法的初步探讨。

Discussion on concept and calculation method of sediment delivery ratio (SDR) of debris flows

Sediment delivery ratio(SDR) is an important concept and parameter in watershed erosion and sediment transport studies.As one of the major forms of soil erosion and sediment transport in the watersheds,debris flows can erode and move significant amount of solid materials from the upstream to the alluvial fan and the main river channel.The concept of debris-flow SDR can link the watershed erosion-sediment generation,debris-flow channel erosion-sedimentation,alluvial fan development,and downstream river channel evolution into a general watershed erosion and sediment transport study framework.Literature survey shows that very few previous studies in this area have been previously reported.In this study,the concept of SDR was introduced to the debris flow sediment transport process,and according to its characteristics,the debris-flow SDR was divided into two consecutive SDRs:(1) The debris-flow channel SDR(Channel-SDR) reflects the capacity of the debris-flow channel in transporting eroded solid materials;and(2) The conjunction SDR(Conjunction-SDR) reflects the capacity of the main river channel in transporting the solid materials contained in the debris flows.In this study,the methods for calculating both Channel-SDR and Conjunction-SDR are developed and applied to a debris-flow event occurred in the Jiangjiagou valley in 2008.The methods are verified by the field data collected from the Jiangjiagou case study,and it is found that the Channel-SDR is equal to 0.14 while the Conjunction-SDR is equal to 0.31.This study also discusses various factors and parameters affecting the SDR calculation results as well as how to improve the debris-flow SDR modeling process.