| 山东丹河2018年洪水沉积特征、物源分析及水文过程重建 |
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| 引用本文： | 李华勇,赵楠,杨艺萍,于正松,孙启发,吴帅虎,张曼,张虎才.山东丹河2018年洪水沉积特征、物源分析及水文过程重建[J].地质力学学报,2022,28(2):226-236. |
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| 作者姓名： | 李华勇 赵楠 杨艺萍 于正松 孙启发 吴帅虎 张曼 张虎才 |
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| 作者单位： | 1.安阳师范学院资源环境与旅游学院，河南 安阳 455000 |
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| 基金项目： | 国家自然科学基金（41807447,41906057,42171217）；河南省自然科学基金青年项目（212300410101）；河南省高等学校重点科研项目（20B170001,21A170002）；安阳市科技攻关项目（2021C01NY035） |
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| 摘 要： | 通过研究现代洪水沉积特征，可重建洪水水文过程，识别泥沙侵蚀源区，既可为防洪水利工程设计提供依据，也可为古洪水层判识建立参考。2018年8月中旬，山东省北部弥河、丹河流域受双台风影响发生洪涝灾害。通过对洪水淹没区进行考察，在下游洪水沉积物保存完好的地点获取21.0 cm长岩芯DH1，并进行粒度、烧失量、磁化率和孢粉分析，结果显示:钻孔岩芯11.5~21.0 cm段为现代土壤层，上部为洪水堆积物，其中0~9.0 cm段是典型洪水粉砂层，粒度较粗，以中—粗粉砂为主，平均砂含量达到14.7%；9.0~11.5 cm段为洪水前期细粒沉积层。根据粒度敏感组分含量变化特征，可将此次洪水过程划分为两个阶段:洪水前期，水动力较弱，在自然条件和人为活动两方面因素共同作用下，滞流现象严重，沉积黏土层；洪水后期，流速显著加快，出现典型洪水粉砂沉积。碳酸盐、有机质含量及孢粉丰度均与粒度负相关，表明弱水动力环境有利于其沉降并富集。土壤表层孢粉组合可较好指示研究区植被分布情况，洪水粉砂层孢粉组合则更能反映流域内植被的整体状况，揭示河流洪水搬运孢粉的能力大于风力；洪水黏土层孢粉组合与研究区内植被分布状况的吻合度较高，明显有别于洪水粉砂层孢粉组合特征，推测洪水前期水位上涨的主因是降水和本地地表径流汇入，因此泥沙和孢粉主要来自研究区内，后期上游客水涌入，带来更多山地植被孢粉信息。研究表明DH1钻孔孢粉组合特征对于传播过程和水动力大小具有良好响应，同时具备识别泥沙侵蚀源区的潜力。磁化率值主要反映成壤强度的大小，在洪水黏土层和粉砂层均表现为稳定的低值，且显著低于接触土壤层，因此可作为判识(古)洪水沉积的有效指标，但其区域普适性有待进一步探讨。
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| 关 键 词： | 山东丹河 洪水沉积 水文过程 物源分析 粒度特征 孢粉 磁化率 |
| 收稿时间： | 2021/8/26 0:00:00 |
| 修稿时间： | 2021/12/3 0:00:00 |
Sedimentary characterization and provenance analysis of the 2018 flooding along the Dan River, Shandong, and the hydrodynamic process reconstruction |
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| LI Huayong,ZHAO Nan,YANG Yiping,YU Zhengsong,SUN Qifa,WU Shuaihu,ZHANG Man,ZHANG Hucai.Sedimentary characterization and provenance analysis of the 2018 flooding along the Dan River, Shandong, and the hydrodynamic process reconstruction[J].Journal of Geomechanics,2022,28(2):226-236. |
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| Authors: | LI Huayong ZHAO Nan YANG Yiping YU Zhengsong SUN Qifa WU Shuaihu ZHANG Man ZHANG Hucai |
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| Affiliation: | School of Resources Environment and Tourism, Anyang Normal University, Anyang 455000, Henan, China;South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, Guangdong, China;Key Laboratory of Ocean and Marginal Sea Geology, Chinese Academy of Sciences, Guangzhou 510301, Guangdong, China;Faculty of Geography, Yunnan Normal University, Kunming 650500, Yunnan, China;Yunnan Key Laboratory of Plateau Geographical Processes and Environmental Changes, Kunming 650500, Yunnan, China; School of Ecology and Environmental Science, Yunnan University, Kunming 650504, Yunnan, China;Institute for Ecological Research and Pollution Control of Plateau Lakes, Yunnan University, Kunming 650504, Yunnan, China |
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| Abstract: | Sedimentary characterization of modern floods helps to reconstruct the hydrologic flood process and spot the source area of sediment erosion. It is of great referential value both to the design of flood-control works and the identification of paleo-flood layers. In mid-August 2018, two typhoons battered the Dan River Basin in northern Shandong, leading to flooding disasters. Based on the research of the flooded area, the boreholeDH1 of 21 cm long was obtained from the downstream with well-preserved flood sediments. The analyses on its grain size, loss on ignition, magnetic susceptibility, and sporo-pollen features, show that the sedimentary cycle under flooding is characterized by fine grains in the lower part and coarse grains in the upper part. Modern soil is developed at a depth of 11.5~21.0 cm; a typical flood silt layer is developed at a depth of 0~9.0 cm, which is relatively coarse in grain size, dominated by medium-to-coarse-grained silt, and with a sand content of 14.7% on average; and a fine-grained sedimentary layer is developed at a depth of 9.0~11.5 cm during the initial period of flooding. According to the various traits of sensitive component contents, the flooding process can be divided into two stages:the relatively weak hydrodynamic force at the earlier stage and the significantly accelerated flow velocity at the later stage; The former is characterized by severe vicious flow and deposition of clays under the combined action of natural conditions and human activities, which can be further divided into two sub-sections of the rising water level and the significant acceleration of flow velocity; The latter result in typical silty deposits from flooding. Carbonate, organic matter content, and sporo-pollen abundance all are negatively correlated with grain size, indicating that the weak hydrodynamic environment is conducive to its deposition and accumulation. The sporo-pollen assemblage of the surface soil can better indicate the distribution of vegetation in the study area, and the sporo-pollen assemblage of the silty layer from flooding can better reflect the overall condition of vegetation in the basin, which has revealed that the river flood is much greater than wind in transporting sporo-pollen. In addition, the sporo-pollen assemblage features in the clayey layer from flooding are in good agreement with the distribution of vegetation in the study area, and obviously different from those of the silty layer from flooding, according to which it is speculated that the primary cause of the water level rise during the initial period of flooding lies in precipitation incorporating with local surface runoff; therefore, the sediment and sporo-pollen are derived from within the study area, and meanwhile the influx of tourists in the later period has brought in more sporo-pollen from mountainous vegetation. The sporo-pollen deposition records from borehole DH1 show that the sporo-pollen assemblage features are in good response to the propagation process and hydrodynamic force, and have the potential to identify the source area of sediment erosion. The magnetic susceptibility mainly reflects the intensity of pedogenesis, and its value for both the clayey and silty layers from flooding is steadily low, significantly lower than that for the soil contact layer. Therefore, it can be used as a reliable indicator for identifying flood deposits, but the geospatial scope of their use needs to be further discussed. |
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| Keywords: | Dan River flood deposit hydrodynamic process provenance analysis grain size features sporo-pollen magnetic susceptibility |
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