【作者】 李铁键；

【导师】 王光谦；

【作者基本信息】 清华大学 ， 水利工程， 2008， 博士

【摘要】 从雨滴降落到地面接触土壤并产生地表径流起,土壤侵蚀和产沙开始发生,之后被剥离的土壤作为泥沙随水流运动,并由沿程冲刷和淤积补充或削减,汇入大江大河,并到达河口进入海洋。泥沙从在地表被剥离到进入海洋的这个生命周期在一个流域中是连续的物理过程。流域泥沙动力学指包括流域面的土壤侵蚀和不同级别沟道河道的泥沙运动在内的流域内泥沙产生、输移和沉积的连续全过程的动力学理论体系与模拟方法。本文以黄河中游多沙粗沙区为例,采用基于动力学的分析与建模方法,实现了流域内泥沙运动全过程模拟。首先,借鉴相关学科已有成果,对多沙粗沙区流域泥沙过程机理进行分析。指出区分不同地貌组成和侵蚀产沙过程,分别建立相应模拟模型并合理集成是完成具有动力学意义的泥沙过程模拟的基础。在所研究区域,这些模型应包括坡面产流产沙模型、沟道水沙演进模型和重力侵蚀模型等。论文将坡面作为基本单元建立了以描述超渗产流过程为主的降雨径流模型,改进并进一步验证了一种基于过程的坡面土壤侵蚀模型。这个土壤侵蚀模型将地表径流作为侵蚀过程的驱动力,考虑了水流强度、土壤可蚀性和微地貌形态的影响。为计算无断面资料沟道中的水流演进和泥沙冲淤过程,提出了采用扩散波方法和悬移质不平衡输沙模式的模拟方法。同时,明确了已有重力侵蚀模型在流域中的运用方式。为使这些模型按水沙运动的顺序集成运行,并提供其在流域尺度应用时需要的计算能力,提出了一种基于二叉树的树状河网编码方法,并在其基础上实现了计算机集群上的流域并行计算。最后,将模型在流域中率定和检验,证明了其模拟流域水沙过程的有效性,并得到了坡面侵蚀、重力侵蚀和沟道侵蚀在流域中的分布及三者的比例关系。进一步,使用模型模拟结果初步解释了流域泥沙过程中尺度现象的形成原因,指出重力侵蚀对尺度现象的贡献最为显著;设定不同情景分析了土壤侵蚀在不同降雨变化下的响应,指出在流域内降雨量减少的情景下,径流量减少的幅度大于侵蚀量的减少幅度。更多还原

【Abstract】 Soil erosion and sediment yield start when rain drops reach ground surface and then runoff yields. Splash detached particles are then carried by flow discharge as sediment, which is replenished or reduced by scouring or deposition along hillslopes, different orders of channels and rivers, and finally enter the sea. The life cycle of sediment from detachment in highlands to deposition in rivers or the sea is a continuous physical process. The subject of river basin sediment dynamics aims at the mechanism and integrated simulation of the whole process of sediment yield, transport and deposition, including soil erosion in highlands, non-equilibrium sediment transport in channels and rivers, etc. Taking the coarse sediment source region in the middle Yellow River as the example, this dissertation achieved the simulation of continous sediment processes based on dynamic principles and modeling approaches.Firstly, the mechanism of sediment processes in the coarse sediment source region was analysed on the basis of existing researches. The fundamental of dynamic modeling of sediment processes was pointed out that different geomorphological positions and different sub-processes must be identified and be modeled separately. In the studied region, the sub-models consist of rainfall- runoff-soil erosion model for hillslopes, flow routing and non-equilibrium sediment transport model for channels, and gravitational erosion model for gully regions.The proposed rainfall-runoff model mainly simulates infiltration-excess runoff in hillslopes, and a process-oriented soil erosion model was improved to simulate hydraulic erosion process by taking surface flow intensity, soil erodibility, and micro relief into account. Flow discharge in channels was routed by using a 1D diffusive wave method, and sediment transport was simulated according to non-equilibrium transport of suspended load. An existing gravitational erosion model was integrated in simulation for river basins by proposing several adptive treatments.To integrate and run the sub-models following the sequence of flow routing and sediment transport among simulation units, a binary tree-based methodology of drainage network codification was proposed. Based on the methodology, a PC cluster-based parrellel computing scheme was achieved following the MPI standard to provide sufficient computing capacity for simulation of large-scale basins.Further more, the integrated model system was calibrated and applied in a watershed and a river basin. The results of hydrographs and sediment graphs in hydrological stations proved effectiveness of the model, and more results were provided including the distributions of hillslope erosion, gravitational erosion, and channel erosion, and their propotions.Finally, simulated results were used to explain the cause of scale effects in sediment processes, and such was revealed that gravitational erosion occurs in specific scales and contributes most to scale effects. Different scenarios were set to analyze the responses of soil erosion and sediment dynamics on the change of rainfall pattern, and it was found out that if rainfall amount decreases and intensity increases, runoff will decrease with amplitude larger than that of the decrease of soil erosion.更多还原