River mouths are highly dynamic environments responding very rapidly to changes in wave energy or river floods. While the morphological response during floods or during marine storm events has been widely documented in the literature, little is known about the mechanisms acting during the co-occurrence of fluvial and marine hazards. This concomitance of river flood and marine storm is quite common in the western Mediterranean Sea, and was the case for the Gloria event, considered to be the most extreme event in recent decades. During this event, monitoring of hydrodynamics and morphological evolution was implemented, making it possible to better understand the impact of concomitant marine storm and fluvial flood during an extreme meteorological event on spit breaching of a small Mediterranean river mouth. Monitoring using a combination of high-resolution hydrodynamic measurements, topographic and bathymetric surveys, and sediment cores was used before, during, and after the storm “Gloria”. The results suggest an amplification of the morphological impact of the events and a different morphogenic response than if each of the events had acted independently on the system. The marine storm, occurring first, weakened the spit and initiated its breaching, which was continued by the extreme fluvial flood, thus leading to the complete destruction of the mouth. The destruction of the spit acted as a sediment source for subaqueous large delta deposition amounting to 50% of the total volume. The contribution of the river, estimated at 30%, was quite low for an exceptional event, showing the importance of locating rainfall in a catchment area controlled by a dam. For this event, extreme morphological evolution was observed, as well as the importance of water levels in the river mouth, which probably increased flood hazards, demonstrating the importance of including the compounding effect of extreme coastal water levels in river flood risk management.

中文翻译：

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评估极端地中海事件对沿海河流出口动态的作用

河口是高度动态的环境，对波浪能或河流洪水的变化反应非常迅速。虽然洪水或海洋风暴事件期间的形态响应已在文献中广泛记录，但对河流和海洋灾害同时发生期间的作用机制知之甚少。这种河流洪水和海洋风暴的同时发生在地中海西部很常见，格洛丽亚事件就是这种情况，被认为是近几十年来最极端的事件。在此次活动中，实施了对水动力和形态演变的监测，以便更好地了解极端气象事件期间伴随的海洋风暴和河流洪水对地中海小河口吐出的影响。在风暴“格洛丽亚”之前、期间和之后使用高分辨率水动力测量、地形和水深测量以及沉积物岩心进行监测。结果表明，与每个事件独立作用于系统的情况相比，事件的形态影响和形态发生反应不同。最先发生的海洋风暴削弱了沙嘴并引发了它的突破，极端的河流洪水继续破坏了它，从而导致了口的完全破坏。沙嘴的破坏作为水下大三角洲沉积物的沉积物来源，占总体积的 50%。河流的贡献，估计为 30%，对于一个特殊事件来说是相当低的，显示了在大坝控制的集水区定位降雨的重要性。对于这一事件，观察到极端的形态演变，以及河口水位的重要性，这可能增加了洪水灾害，证明了将极端沿海水位的复合效应纳入河流洪水风险管理的重要性。