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| 沙漠河流辫状河型发育的动力机制 ——以黄河乌兰布和沙漠河段为例 | |
| 其他题名 | Mechanism of the evolution of the desert braided channel in the Ulan Buh Desert Reach of the Yellow River, China |
| 李永山 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 拓万全 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 沙漠河流具有大规模风沙入汇、沙质河床发育、主河槽横向摆动频繁、分汊数量多的特点，普遍发育成辫状河型。沙漠河流辫状河道形态的发育不仅受水沙条件、边界条件以及基准面等因素影响，风沙也是沙漠河流辫状河型发育的重要影响因素。黄河上游的乌兰布和沙漠河段属于典型的沙漠河流，受乌兰布和沙漠风沙入黄的影响发育成沙质辫状河道。因此，本文以黄河乌兰布和沙漠河段为研究对象，通过对其区域风沙活动特征、河道泥沙粒度以及近50年的水沙资料与河道断面数据的分析，探讨了沙漠河流辫状河型发育机制，并分析了黄河乌兰布和沙漠河段辫状河道形态的近50年的演变特征、趋势及其驱动因素。主要得出以下几点认识：1. 在沙漠河流中，除水沙条件、边界条件与基准面以外，风沙也是河道形态发育演变的驱动因子，松散非粘滞性的风沙聚岸为河道横向侵蚀拓宽提供了非约束性的边界条件，风沙入河为沙质河床与河道辫状形态的发育提供了物质基础。风沙入河与水沙条件是调控沙漠河流辫状河道形态发育与演变的主要驱动因素。2. 河流的横向侵蚀、搬运与堆积作用是沙漠河流辫状河道发育的动力条件。在河流横向侵蚀和河床横向坡度驱动下，河道横向冲淤与摆动演变剧烈，覆岸沙丘不断坍塌进入河床，河道不断拓宽，进而辫状河道形态发育。河流流量越大，流水对覆岸沙丘侵蚀愈加剧烈，风沙入河量越大，河道横向摆动更加剧烈，辫状河道越发育。3. 黄河乌兰布和沙漠河段在风沙与水沙的调控下，近50年辫状河道形态的演变过程可分为两个阶段：1966-1990年，黄河水沙条件呈“大流量-低含沙量特点，河流横向侵蚀、搬运与堆积过程强烈，河道横向摆动频繁，风沙入黄量大，辫状河道发育强烈。1991～2013年，随着黄河流量减小，尤其1992～2000年，水沙关系表现出“小流量-高含沙量”，河道横向摆动能力减弱，黄河主河槽远离左岸乌兰布和沙漠杀气，年，水沙关系表现出“小流量-高含沙量”，河道横向摆动能力减弱，黄河主河槽远离左岸乌兰布和沙漠沙丘，河道萎缩变窄，河道分汊数目明显减少，黄河乌兰布和沙漠河段辫状河型有向单一河道的弯曲型河流演变的趋势。 |
| 英文摘要 | Rivers flow through sand dunes and develop as braided stream, which is characterized by the infusion of large aeolian sands into the river, sandy riverbed development, the frequently lateral shift of the channel, and numerous secondary channels. The Ulan Buh Desert Reach of the Yellow River which flow from south to north across the Ulan Buh Desert, forming the braided channel, is selected as the typical study area of braided channel of rivers that flows across sand dunes. Based on wind-sand activity in this region, particle size distribution of the sediments in the desert braided channel, cross sections, discharges and suspended concentrations of the past 50 years, the study discussed the mechanism of the evolution of the Ulan Buh Desert braided channel of the Yellow River, and illuminated change characteristics, the developmental trend and the driving factors of the Ulan Buh Desert braided channel of the Yellow River. The results show that: 1. In desert-river, aeolian sand is the vital driving factor for the braided channel besides discharge and sediment concentration, boundary conditions and base level. Loose and non-viscosity sands for the lateral broaden of the channel provides a constraint boundary condition, the infusion of sands into the river is the base for developing sandy river and braided channel. Water and sediment and the infusion of aeolian sands into the river are the main factors for regulating the evolution of the braided desert channel. 2. River lateral erosion, transportation and accumulation function is the dynamic process of the desert braided river channel development. Due to the action of lateral erosion and the lateral bed slope, channel lateral scouring and filling frequently, and sand dunes constantly collapsed into the river，the channel constantly expanding, so the braided channel develops. When the discharge increases, the more aeolian sands are eroded into the river bed, the more typical the braided channel develops. 3. Under the regulation of the aeolian sands, water and suspended sediments, in the past 50 years the Ulan Buh Desert braided channel of the Yellow River went through two stages of development: from the year of 1966 to 1990, with the high flow and low wash-load sediment concentration, the river lateral erosion, transportation and accumulation process was strong, and furthermore the frequently lateral shift of the channel and the infusion of aeolian sands into the Yellow River led to the development of braided channel; from the year of 1991 to 2013, especially from the year of 1992 to 2000, with the low flow and high wash-load sediment concentration, a reduction in the lateral channel shift rate and the shifting of the main active channel away from the eolian-dune-covered bank caused the shrinking of the braided channel and a reduction of the channel number, which led to the main active channel evolving into a meandering channel. |
| 中文关键词 | 沙漠河流 ; 辫状河型 ; 黄河乌兰布和沙漠河段 ; 风沙活动 |
| 英文关键词 | Desert river the braided channel the Ulan Buh Desert Reach of the Yellow River China aeolian |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287696 |
| 推荐引用方式 GB/T 7714 | 李永山. 沙漠河流辫状河型发育的动力机制 ——以黄河乌兰布和沙漠河段为例[D]. 中国科学院大学,2016. |
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