Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976-2013): Dominant roles of riverine discharge and sediment grain size
Stepwise morphological evolution of the active Yellow River (Huanghe) delta lobe (1976-2013): Dominant roles of riverine discharge and sediment grain size
复制标题
活跃黄河三角洲叶的逐步形态演化（1976-2013）：河流流量和沉积物粒度的主导作用
DOI：
10.1016/j.geomorph.2017.04.042
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发表时间：
2017
期刊：
影响因子：
3.9
通讯作者：
Wang Houjie
中科院分区：
文献类型：
--
作者：
Wu Xiao;Bi Naishuang;Xu Jingping;Nittrouer Jeffrey A.;Yang Zuosheng;Saito Yoshiki;Wang Houjie
目前活跃的黄河三角洲是1976年人为改道后形成的。目前三角洲叶形态演化的过程和驱动力尚不清楚。本文研究了黄河三角洲活动性叶片的陆地和水下组分的逐步形态演化过程，并说明了河流流量和泥沙粒度在三角洲演化中起主导作用。根据河口上游约100 km的最后一个测量站利津站的流量和输沙量，计算了维持三角洲稳定的临界输沙量。结果表明，活动三角洲瓣的发育经历了四个连续的阶段，其中包括陆上和水下成分。在河道迁移后的第一阶段（1976-1981年），非河道化的水流加剧了河道内和利津站至河口河漫滩内的淤积。因此，由利津站获得的河流输入计算的临界输沙量最大。然而，该阶段的实际输沙量（0.84 Gt/yr）是维持陆上活动区所需临界输沙量（~ 0.35 Gt/yr）的两倍多，有利于黄河陆上三角洲的快速向海进积。在第二阶段（1981-1996年），工程促进的河道化水流和输入海悬沙中位粒径的增大导致维持三角洲稳定的临界输沙量减小到0.29 Gt/yr。该阶段活动三角洲叶片仍以11.9 km2/yr的吸积速率向海推进，利津站年输沙量为0.55 Gt/yr。1996 ~ 2002年，临界输沙量进一步减小至0.15 Gt/yr，泥沙粒径增大至22.5 μm；然而，由于泥沙供应不足，三角洲遭受净侵蚀（0.11 Gt/yr）。最近阶段（2002 ~ 2013年），由于大坝整治对下游河道的强烈冲刷，泥沙相对较粗，有效降低了临界输沙量至0.06 Gt/yr，远低于利津站相应的输沙量（~ 0.16 Gt/yr）。因此，黄河三角洲陆上过渡到一个轻微的增生阶段。总体而言，黄河活动三角洲的演化与河流水沙流量密切相关。维持陆上三角洲稳定的输沙量是不稳定的，随河道形态和泥沙粒度的变化而变化。人类影响的河流输沙量和粒度组成在活动三角洲叶的逐步形态演化中起主导作用。
The presently active Yellow River (Huanghe) delta lobe has been formed since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaerial and the subaqueous components, and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution. The critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station Lijin, the last gauging station approximately 100 km upstream from the river mouth. The results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages. During the first stage (1976–1981) after the channel migration, the unchannelized river flow enhanced deposition within the channel and floodplain between Lijin station and the river mouth. Therefore, the critical sediment supply calculated by the river inputs obtained from station Lijin was the highest. However, the actual sediment load at this stage (0.84 Gt/yr) was more than twice of the critical sediment load (~ 0.35 Gt/yr) for sustaining the active subaerial area, which favored a rapid seaward progradation of the Yellow River subaerial delta. During the second stage (1981–1996), the engineering-facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0.29 Gt/yr. The active delta lobe still gradually prograded seaward at an accretion rate of 11.9 km2/yr at this stage as the annual sediment load at Lijin station was 0.55 Gt/yr. From 1996 to 2002, the critical sediment load further decreased to 0.15 Gt/yr with the sediment grain size increased to 22.5 μm; however, the delta suffered net erosion because of the insufficient sediment supply (0.11 Gt/yr). In the most recent stage (2002 − 2013), the intensive scouring of the lower river channel induced by the dam regulation provided relatively coarser sediment, which effectively reduced the critical sediment load to 0.06 Gt/yr, much lower than the corresponding sediment load at Lijin station (~ 0.16 Gt/yr). Consequently, the subaerial Yellow River delta transitioned to a slight accretion phase. Overall, the evolution of the active Yellow River delta is highly correlated to riverine water and sediment discharge. The sediment supply for keeping the subaerial delta stability is inconstant and varying with the river channel morphology and sediment grain size. We conclude that the human-impacted riverine sediment discharge and grain-size composition play dominant roles in the stepwise morphological evolution of the active delta lobe.