Abstract The Bengal delta, the largest delta on the Earth, is subject to a marked coastal flooding hazard and associated with widespread vulnerability. The situation will expectedly deteriorate in the ongoing context of sea level rise. This sea level rise will not only have a direct effect on the coastal flooding, but will also have indirect effects, through the alteration of the coastal hydrodynamics. In the present study, we investigate the impact of sea level rise on tide, which is the largest source of variability of sea level along the macro-tidal coast of Bengal delta. Through a comprehensive modelling framework comprising the coastal delta, major estuaries, as well as the intricate hydraulic network of the delta, we assess the future changes of tidal properties to be expected for various sea level rise scenarios, representative of the end of the 21st century and beyond. It is found that the effect is large, and regionally dependent. Over both the south-western and south-eastern parts of the delta, the amplitude of the tide is expected to increase when the sea level is higher, which is bound to aggravate the tidal flooding hazard. In contrast, the central part of the delta will potentially experience massive flooding of river banks and adjoining lands in the scenarios exceeding 0.5 m of sea level rise. Consequently, this flooding induces a decay of the tidal amplitude in the central part. Our study shows that the tidal modulation is a significant ingredient that needs to be accounted for in the evolution of the future hydrodynamics of the Bengal delta. The friction-dominated and regionally contrasting damping and amplification mechanism also underscores the potential application of managed realignment strategy for a sustainable delta management in the future.

中文翻译：

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海平面上升导致孟加拉三角洲沿岸的潮汐调制

摘要 孟加拉三角洲是地球上最大的三角洲，面临着明显的沿海洪水灾害，并且普遍存在脆弱性。在海平面持续上升的背景下，情况预计会恶化。这种海平面上升不仅会对沿海洪水产生直接影响，还会通过改变沿海水动力产生间接影响。在本研究中，我们调查了海平面上升对潮汐的影响，潮汐是孟加拉三角洲大潮汐沿岸海平面变化的最大来源。通过由沿海三角洲、主要河口以及三角洲错综复杂的水力网络组成的综合建模框架，我们评估了各种海平面上升情景下潮汐特性的未来变化，21 世纪末及以后的代表。发现效果大，且具有区域依赖性。在三角洲的西南和东南部，随着海平面的升高，潮汐的振幅预计会增加，这势必会加剧潮汐洪水的危害。相比之下，在海平面上升超过 0.5 m 的情况下，三角洲的中部可能会经历河岸和毗邻土地的大规模洪水。因此，这种洪水会导致中部潮汐振幅的衰减。我们的研究表明，潮汐调制是孟加拉三角洲未来流体动力学演变中需要考虑的重要因素。