Deltas are fascinating landforms subject to fluvial and marine forcing. Bifurcations are common features in deltas, governing the distribution of water and sediment fluxes among the distributary channel network. Recently, it has been observed that tide‐influenced deltas tend to display less numerous but more stable branches in comparison to their riverine counterparts. River bifurcations subject to unidirectional flow have been widely studied in the last decades. In contrast, the acting physical mechanisms and factors controlling the stability of bifurcations in tide‐influenced deltas are still not well understood, and a theoretical framework is still lacking. In order to fill this gap and understand how the stability and evolution of bifurcations in distributary deltaic systems could be affected by the tides, we investigate, through an analytical model, the equilibrium configurations and stability of tidal bifurcations under the hypothesis of small monochromatic tidal oscillations. In particular, we build on previous works on river bifurcations, incorporating the solution for the equilibrium of a single‐river‐dominated estuary. We find that higher tidal amplitudes and a closer proximity of the junction node to the sea tend to hamper the development of unbalanced solutions, reducing the asymmetries in water and sediment fluxes between branches. This stabilizing effect exerted by the tidal action is associated with the erosive character of the tidal currents that promotes channel deepening and increases the capacity of the system to keep morphodynamically active both bifurcates in comparison with the purely fluvial case. Preliminary field observations of natural deltas corroborate our findings.

中文翻译：

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小潮汐波动对分叉稳定性和平衡构型的影响

三角洲是受河流和海洋强迫作用的迷人地貌。分叉是三角洲的共同特征，支配着分布河道网络中水和泥沙通量的分布。最近，已经观察到，受潮汐影响的三角洲与河流沿岸的三角洲相比，其分支较少，但更稳定。在过去的几十年中，对单向流动的河流分岔进行了广泛的研究。相比之下，潮汐影响三角洲中分叉稳定性的作用物理机制和因素仍未得到很好的理解，并且仍然缺乏理论框架。为了填补这一空白，并了解潮汐如何影响分流三角洲系统分叉的稳定性和演化，我们研究了 通过分析模型，在小单色潮汐振荡的假设下，潮汐分叉的平衡构型和稳定性。特别是，我们在先前关于河流分叉的工作的基础上，结合了以单一河流为主的河口平衡的解决方案。我们发现，较高的潮汐幅度和交界处与海的距离更近，往往会阻碍解决方案不平衡的发展，从而减少分支之间水和泥沙通量的不对称性。与纯河流情况相比，潮汐作用所产生的这种稳定作用与潮汐流的侵蚀性特征有关，潮汐流的侵蚀性特征促使通道加深并增加了系统保持两个分叉的形态动力学活性的能力。