Hydro-morphodynamics triggered by extreme riverine floods in a mega fluvial-tidal delta
Hydro-morphodynamics triggered by extreme riverine floods in a mega fluvial-tidal delta
复制标题
大型河流潮汐三角洲极端河流洪水引发的水流形态动力学
DOI：
10.1016/j.scitotenv.2021.152076
复制
发表时间：
2022
影响因子：
9.8
通讯作者：
Liu, Xiaoqiang
中科院分区：
文献类型：
--
作者：
Wang, Jie;Dai, Zhijun;Fagherazzi, Sergio;Zhang, Xiaohe;Liu, Xiaoqiang
维持巨型三角洲的增生和进积对其地貌稳定性和生态至关重要。极端的河流洪水会扰乱水力沉积动力学，对三角洲景观造成巨大破坏，例如三角洲侵蚀。如今，大多数巨型三角洲都面临着沉积物匮乏的问题。了解极端洪水的影响是确定三角洲系统长期命运的首要任务。在此，我们利用代尔夫特3D模型和现场数据研究了2016年长江三角洲南航道（SP）极端河流洪水的水力学和形态动力学。结果表明，极端洪水会增加河口内河道和河口坝的水位、流速和河床剪应力，而洪水对近海地区的影响较弱。高能洪水引发强烈的潮汐不对称和欧拉余流，加剧下游悬浮泥沙输送和底部河床侵蚀。与2016年特大洪水时期相比，洪水过后净侵蚀量向海减弱，河口内河道、河口坝和近海区域相应的平均测深侵蚀厚度分别为19.97厘米、12.71厘米和4.62厘米。尽管向海沉积斑块是由于冲刷作用较低和沉积物汇聚所致。较深河道的水动力增量更为显着，而浅滩和较深区域受到强烈侵蚀，在-5 m至-6 m等深线之间侵蚀最低。这些结果进一步阐明了水深模式，其中突出显示了极端河流洪水可能会放大此类大型河流潮汐三角洲沉积物不足的风险。
Maintaining accretion and progradation in a mega delta is crucial to its geomorphic stability and ecology. Extreme riverine floods can disturb hydro-sediment dynamics with great damage to the deltaic landscape, as for instance deltaic erosion. Nowadays, most mega deltas suffer from sediment starvation. Understanding the impact of extreme floods is a priority to determine the long-term fate of deltaic systems. Herein, we used the Delft 3D model and field data to study the hydraulics and morphodynamics of the 2016 extreme riverine floods in the South Passage (SP) of the Yangtze Delta. Results reveal that extreme floods can increase water levels, velocities, and bed shear stresses in an inner estuarine channel and mouth bar, while the flood has a weak effect in offshore areas. High-energy floods trigger strong tidal asymmetry and Euler residual currents, which intensifies downstream suspended sediment transport and bottom riverbed erosion. In comparison with those during extreme floods in 2016, net erosion after floods passed away was generated with seaward weakened magnitudes, the corresponding mean bathymetric erosion thickness was 19.97 cm, 12.71 cm and 4.62 cm in inner estuarine channel, mouth bar and offshore area, respectively. Even though the seaward deposition patches were due to lower scouring effect and converged sediment. Hydrodynamic increments in deeper channels were more significant, while shoals and deeper areas were strongly eroded with the lowest erosion between −5 m to −6 m isobath. These results further clarified the bathymetric patterns with highlights of extreme riverine floods that can amplify the sediment-insufficient risks in such mega fluvial-tidal delta.