沙棘柔性坝拦沙机理及其拦沙效应优化的试验研究与数学模拟

The seabuckthorn flexible dam is a newly biotic measure in controlling soil and water loss and ecological rehabilitation, and recently, its application is primarily used increasingly in the Pisha sandstone area named as "the earth environmental cancer" all the time. Yet, in abroad, there are not researches on the seabuckthorn flexible dam so far, in China current studies on the trapping sediment mechanism of the seabuckthorn flexible dam were also scarce and not systematically deep, and while studies on the optimizing mathematical model of sediment retention effects of the seabuckthorn flexible dam were vancancies. In this research, based on field small catchment prototype sediment and water observations and field sediment-flow model tests, the methods of therotical analysis and mathematical simulation would be used, major factors affecting the seabuckthorn flexible dam trapping sediment would be identified, the respond of the seabuckthorn flexible dam to different sediment-flow conditions in the upper gully in small catchment in Pisha sandstone area would be revealed, and the mechanism of the seabuckthorn flexible dam on trapping sediment woule be also systematically and deeply analysed and resolved. Furthemore, in order to provide theoretical guidance and proof, the optimization mathematical model of sediment retention effects of the seabuckthorn flexible dam based on cost-benefit under the impacts and limitation of different major factors woule be explored and established using the combination of sediment-flow mathematical model and the multi-objectives function optimizing theory and technique of the operation research discipline. Aims of this study are to both help theoretically deepen the understand and konowledgement of people to the plant flexible engineering in retarding flood and trapping sediment and provide theoretical proof and guidance for the optimizing design and planting of the seabuckthorn flexible dam in practice.

沙棘"柔性坝"是一种治理水土流失与修复生态的新型生物措施，近年来在有"地球环境癌症"之称的砒砂岩地区初步得到了广泛应用。国外目前尚没有关于沙棘柔性坝的研究报道，国内则缺乏对沙棘柔性坝拦沙机理系统而深入的研究，而对于沙棘柔性坝拦沙效应优化方面的研究则更是空白。本研究基于野外原型试验小流域场次含沙洪水监测及野外水沙模型试验，采取理论分析与数学模拟的方法，辨识沙棘柔性坝拦沙效应的主要影响因子，揭示沙棘柔性坝对砒砂岩区小流域沟道上游不同水沙条件的响应关系，系统深入地解析沙棘柔性坝的拦沙机理；尝试将水沙数学模型与运筹学中的多目标函数优化理论技术相结合，探索建立在主要因子影响与约束下，基于成本-效益(cost-benefit)的沙棘柔性坝拦沙效应优化数学模型。本研究在理论上有助于深化人们对植物柔性工程滞洪拦沙作用与机理的理解与认识，在实践上可为沙棘柔性坝的优化布置与栽植提供理论依据。

黄河的根本问题是泥沙问题，钱宁经过野外考察后认为特别是泥沙颗粒大于0.05mm以上的粗泥沙。位于晋、陕、蒙交界区域约1.67万km2的砒砂岩区，是入黄粗沙的主要来源区。该区剧烈的水土流失给黄河下游河道造成了严重的泥沙淤积，因而该区的土壤侵蚀与水土流失治理一直是水保专家共同关注的热点。沙棘“柔性坝”是一种治理水土流失与修复生态的新型生物措施，近年来在有“地球环境癌症”之称的砒砂岩地区初步得到了广泛应用。国外目前尚没有关于沙棘柔性坝方面的研究报道，国内也缺乏对沙棘柔性坝拦沙机理及其拦沙效应优化方面的报道。本研究基于野外观测及水沙模型试验，采取理论分析与数学模拟的方法，辨识了沙棘柔性坝拦沙效应的主要影响因子，揭示了沙棘柔性坝对不同水沙条件的响应及其特征；基于研究区域的相关数据，运用AnnAGNPS模型对砒砂岩小流域的产沙进行了模拟，构建了砒砂岩小流域模型数据库，分析了其产沙特性与特征，并探讨了砒砂岩区小流域沟道的产沙机理。基于实验数据，系统深入地解析了沙棘柔性坝的拦沙机理及其影响因素，并探讨了主要影响因子之间的关系。在野外试验基地，开展了沙棘柔性坝清水与含沙水流试验，探讨了不同种植参数下，沙棘柔性坝对水流特性的影响及沙棘植物柔性坝不同断面上泥沙颗粒级配的变化。并运用VFSMOD模型对沙棘柔性坝的拦沙效应进行了优化模拟，并对其主要影响因素进行了分析，对沙棘-灌草复合带相关设计参数进行了探讨，并给出了砒砂岩区小流域沟道栽植沙棘柔性坝时的优化参数及取值范围。在野外试验的基础上，还额外对沙棘灌草混合植被过滤带对砒砂岩缓坡区域上的泥沙及农业非点源污染物的消减作用进行了模拟。这些成果对于深入理解沙棘柔性坝的拦沙机理、拦沙效应的优化、对NPSP的消减作用、及其后期推广应用都具有重要的科学意义与实践价值。