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Temporal and spatial patterns of sedimentation within the batture lands of the middle Mississippi River, USA

机译：美国密西西比河中部营地内沉积的时空格局

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Sediment deposition and storage are important functions of batture lands (the land between the channel's low-water elevation and the flood mitigation levee). However, sedimentation processes within these areas are not fully understood. In this paper, we explore the spatiotemporal patterns, rates, and volume of sedimentation within the batture lands along the middle Mississippi River (MMR; between the confluence of the Missouri and Ohio rivers) using three approaches: (1) comparison of historical to modern elevation data in order to estimate long-term (100 yr) sedimentation rates; (2) estimation of medium-to short-term (50 yr) sedimentation rates using dendrogeomorphological methods; and (3) geomorphic change detection (GCD) software to estimate short-term sedimentation rates (similar to 12 yr), spatial patterns of deposition, and volumes of geomorphic change within the batture lands. Comparison of long-to short-term sedimentation rates suggests up to a 300% increase in batture land sedimentation rates (from 6.2 to 25.4 mm yr(-1)) despite a substantial decrease in the MMR's suspended-sediment load (70%) attributed largely to sediment trapping by dams during the second half of the twentieth century. The increase in MMR batture land sedimentation rates are attributed to at least two potential mechanisms: (1) the above average frequency and duration of low-magnitude floods (2-yr and = 5-yr flood) during the short-term assessment periods which allowed for more suspended sediment to be deposited within the batture lands; and (2) the construction of levees that substantially reduced the floodplain area (similar to 75%) available for storage of overbank deposits increasing the vertical accumulation and consequently the detectability of a given volume of sediment The GCD estimated batture land sediment volumes were similar to 9.0% of the suspended load at St Louis. This substantial storage of sediment (similar to 8.5 Mt yr(-1)) along the MMR suggests batture lands are an important sink for suspended sediments. (C) 2018 Elsevier B.V. All rights reserved.
机译：沉积物的沉积和存储是补给土地（河道低水高程与防洪堤之间的土地）的重要功能。但是，这些区域内的沉积过程尚未完全了解。在本文中，我们使用三种方法探讨了密西西比河中部（MMR；密苏里河与俄亥俄州河之间的汇合处）的营地内的时空格局，沉积速率和沉积量：（1）比较历史与现代高程数据，以估计长期（> 100年）的沉积率； （2）使用树状地貌方法估算中短期（<50年）的沉积速率； （3）地貌变化检测（GCD）软件来估算短期沉积速率（类似于12年），沉积的空间模式以及营地内地貌变化的数量。比较长期和短期的沉积率表明，尽管MMR的悬浮泥沙量显着降低（> 70％），但营地的沉积率却增加了300％（从6.2到25.4 mm yr（-1））。很大程度上归因于20世纪下半叶大坝捕获的泥沙。 MMR营地土地沉积率的增加至少归因于两个潜在机制：（1）在短期评估中，低震级洪水（> 2年且<= 5年洪水）的平均频率和持续时间均高于上述平均水平允许更多悬浮悬浮物沉积在营地内的时期； （2）堤防建设大大减少了洪泛区面积（约占75％），可用于存储过岸沉积物，从而增加了垂直积累，因此可检测到一定量的沉积物。GCD估算的滩涂土地沉积物量与圣路易斯市9.0％的悬吊货物。沿MMR的大量沉积物存储（类似于8.5 Mt yr（-1））表明，陷地是悬浮沉积物的重要汇。 （C）2018 Elsevier B.V.保留所有权利。

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