State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China.
Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
Sci Rep. 2017 Sep 5;7(1):10535. doi: 10.1038/s41598-017-10958-y.
Deltas are widely threatened by sediment starvation and climate change. Erosion potential is an important indicator of delta vulnerability. Here, we investigate the erosion potential of the Yangtze Delta. We found that over the past half century the Yangtze's sediment discharge has decreased by 80% due to the construction of >50,000 dams and soil conservation, whereas the wind speed and wave height in the delta region have increased by 5-7%, and the sea level has risen at a rate of 3 mm/yr. According to hydrodynamic measurements and analyses of seabed sediments, the period when bed shear stress due to combined current-wave action under normal weather conditions exceeds the critical bed shear stress for erosion (τ ) accounts for 63% of the total observed period on average and can reach 100% during peak storms. This explains why net erosion has occurred in some areas of the subaqueous delta. We also found that the increase with depth of τ is very gradual in the uppermost several metres of the depositional sequence. We therefore expect that the Yangtze subaqueous delta will experience continuous erosion under sediment starvation and climate change in the next decades of this century or even a few centuries.
三角洲广泛受到泥沙供应不足和气候变化的威胁。侵蚀潜力是衡量三角洲脆弱性的一个重要指标。在这里，我们研究了长江三角洲的侵蚀潜力。我们发现，在过去的半个世纪里，由于建设了 5 万多座大坝和进行了土壤保持措施，长江的泥沙排放量减少了 80%，而该地区的风速和波高增加了 5-7%，海平面以每年 3 毫米的速度上升。根据水动力测量和海底沉积物分析，在正常天气条件下，由水流和波浪共同作用产生的床面剪切应力超过侵蚀临界床面剪切应力（τ）的时期平均占总观测期的 63%，在高峰风暴期间甚至可达 100%。这解释了为什么在水下三角洲的一些地区会发生净侵蚀。我们还发现，在沉积序列的最上部几米，τ随深度的增加非常缓慢。因此，我们预计在本世纪的未来几十年甚至几个世纪里，在泥沙供应不足和气候变化的情况下，长江水下三角洲将持续受到侵蚀。
