River delta degradation has been caused by extraction of natural resources, sediment retention by reservoirs, and sea-level rise. Despite global concerns about these issues, human activity in the world’s largest deltas intensifies. Harbour development, construction of flood defences, sand mining and land reclamation emerge as key contemporary factors that exert an impact on delta morphology. Tides interacting with river discharge can play a crucial role in the morphodynamic development of deltas under pressure. Emerging insights into tidal controls on river delta morphology suggest that—despite the active morphodynamics in tidal channels and mouth bar regions—tidal motion acts to stabilize delta morphology at the landscape scale under the condition that sediment import during low flows largely balances sediment export during high flows. Distributary channels subject to tides show lower migration rates and are less easily flooded by the river because of opposing non-linear interactions between river discharge and the tide. These interactions lead to flow changes within channels, and a more uniform distribution of discharge across channels. Sediment depletion and rigorous human interventions in deltas, including storm surge defence works, disrupt the dynamic morphological equilibrium and can lead to erosion and severe scour at the channel bed, even decades after an intervention.

三角洲的退化是由于自然资源的开采，水库的泥沙淤积和海平面上升引起的。尽管全球对这些问题感到担忧，但世界上最大三角洲的人类活动仍在加剧。港口发展，防洪建设，采砂和土地开垦已成为影响三角洲形态的重要当代因素。潮汐与河水相互作用可在压力作用下的三角洲形态动力学发展中发挥关键作用。关于河三角洲形态的潮汐控制的新兴见解表明，尽管潮汐通道和河口坝地区有活跃的形态动力学，潮汐运动在景观尺度上起到稳定三角洲形态的作用，条件是低流量时的泥沙进口在高流量时的泥沙出口基本平衡。流。受潮汐影响的分流河道显示出较低的迁移率，并且由于河流流量与潮汐之间存在相反的非线性相互作用，因此不易被河流淹没。这些相互作用导致通道内的流量发生变化，并使通道之间的流量分布更加均匀。三角洲的沉积物耗竭和严格的人工干预（包括风暴潮防御工作）破坏了动态形态平衡，甚至在干预后数十年也可能导致河床侵蚀和严重冲刷。