Angamuthu B, Darby S E, Nicholls R J
Geography and Environment, University of Southampton, Southampton SO17 1BJ, UK.
Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK.
Proc Math Phys Eng Sci. 2018 Nov;474(2219):20180396. doi: 10.1098/rspa.2018.0396. Epub 2018 Nov 7.
The world's deltas are at risk of being drowned due to rising relative sea levels as a result of climate change, decreasing supplies of fluvial sediment, and human responses to these changes. This paper analyses how delta morphology evolves over multi-decadal timescales under environmental change using a process-based model. Model simulations over 10 years are used to explore the influence of three key classes of environmental change, both individually and in combination: (i) varying combinations of fluvial water and sediment discharges; (ii) varying rates of relative sea-level rise; and (iii) selected human interventions within the delta, comprising polder-dykes and cross-dams. The results indicate that tidal asymmetry and rate of sediment supply together affect residual flows and delta morphodynamics (indicated by sub-aerial delta area, rates of progradation and aggradation). When individual drivers of change act in combination, delta building processes such as the distribution of sediment flux, aggradation, and progradation are disrupted by the presence of isolated polder-dykes or cross-dams. This suggests that such interventions, unless undertaken at a very large scale, can lead to unsustainable delta building processes. Our findings can inform management choices in real-world tidally-influenced deltas, while the methodology can provide insights into other dynamic morphological systems.
由于气候变化导致相对海平面上升、河流沉积物供应减少以及人类对这些变化的应对措施，世界上的三角洲面临被淹没的风险。本文使用基于过程的模型分析了在环境变化下三角洲形态在数十年时间尺度上是如何演变的。通过10年的模型模拟来探究三类关键环境变化单独以及组合起来的影响：（i）河流流量和输沙量的不同组合；（ii）相对海平面上升的不同速率；（iii）三角洲内选定的人类干预措施，包括圩垸堤坝和跨河大坝。结果表明，潮汐不对称性和泥沙供应速率共同影响剩余水流和三角洲地貌动力学（以陆地三角洲面积、进积速率和加积速率表示）。当单个变化驱动因素共同作用时，诸如泥沙通量分布、加积和进积等三角洲形成过程会因孤立的圩垸堤坝或跨河大坝的存在而受到干扰。这表明，除非大规模实施，否则此类干预措施可能导致不可持续的三角洲形成过程。我们的研究结果可为实际受潮汐影响的三角洲的管理决策提供参考，而该方法可为其他动态地貌系统提供见解。
