Mud deposits on Cassino beach are associated with waves generated from storms during cold front passages and extratropical cyclones from the southern quadrant. During such episodes fluid mud deposited at the shoreface and surf zone is transported towards the surf zone and the sandy beach prism. The first mention on the origin of mud has always attributed a source exclusively natural for the deposits. However, new interpretations and recent data indicate that the increase in dredged volumes over the years increased the frequency of mud depositions. In order to verify this association, records of dredged and discarded volumes in the Port of Rio Grande and Cassino beach shoreface were analyzed. Maps of bottom types, silt and clay ratio, and fluid mud thickness obtained from superficial samples and sediment cores between 4 and 15 m water depth at the time of the 1998 impact were also reanalyzed. Current conditions near the dumping sites in the estuary and inner shelf in 1998 were reconstructed by hindcast based on reanalysis data and an ADCP anchored 15 m off the Rio Grande coast. In order to verify the effect of the passage of a cold front on the bottom near the ocean dumping site, data from two mooring stations made on the crest and swale of a sand ridge field were considered. To further understand the disposal of the dredged material, a particle transport model was created for two periods related to the depositional events. In the period of 1998, it was simulated the disposal of dredged material on two locations, one with the disposal of 640,000 m 3 of sediment inside the estuary at 8 m of depth and, the other, with 2.3 million m 3 of disposal material, at 13 m depth in the shoreface. The simulation at depth of 19 m, for the dumping site of 2014 considered the disposal of 1,000.000 m 3 at 19 m water depth. The occurrence of massive concentrations of an estuarine gastropod associated with the deposits at the beach led to a literature search on their occurrence in the area after researches carried out for more than three decades on the fauna ecology of sandy beaches. From the 1970s onwards, dredged volumes intensify and were deposited into the estuary and ocean using Hopper dredges. There was an increase in episodes of mud deposition at CB. The sedimentation patterns after dredging operations indicate that natural sedimentary processes are altered in a transient way. Currents generated by winds and storms in both quadrants north and south provide conditions of instability of fine sediments in the disposal sites with flow components parallel and also direct to the coast regardless of wave action. Hydrodynamic modeling indicates that sediments disposed into both the estuary and the shoreface during northeast and southern winds have the potential to be driven towards the beach. The massive deposition of millions of organisms after dredging events is not a natural process and is an indication of the dredging activities. Dredging can be an important part of the environmental impact because the natural accumulation process is enhanced by intense pulses of fine sediments in short time favoring more frequent depositions since the historical and current disposal sites are not appropriate. Negative environmental impacts are related to beach usage since it affects sunbathers, surfers, vehicle traffic, morphodynamic changes, and massive mortality of the benthic fauna.

中文翻译：

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卡西诺海滩的泥浆沉积物：疏浚的作用

卡西诺海滩上的泥浆沉积物与冷锋通道期间风暴和来自南象限的温带气旋产生的波浪有关。在这种情况下，沉积在岸面和冲浪带的流体泥浆被输送到冲浪带和沙滩棱柱。第一次提到泥浆的起源总是归因于沉积物的纯天然来源。然而，新的解释和最近的数据表明，多年来疏浚量的增加增加了泥浆沉积的频率。为了验证这种关联，分析了里奥格兰德港和卡西诺海滩岸面的疏浚和丢弃量记录。底部类型、淤泥和粘土比例的地图，还重新分析了 1998 年撞击时从 4 至 15 m 水深的表层样品和沉积物岩心获得的流体泥浆厚度。1998 年河口和内陆架倾倒场附近的现状是根据再分析数据和锚定在里奥格兰德海岸 15 m 处的 ADCP 通过后报重建的。为了验证冷锋在海洋倾倒场附近的底部通过的影响，考虑了在沙脊场的顶部和洼地制作的两个系泊站的数据。为了进一步了解疏浚材料的处置，创建了与沉积事件相关的两个时期的粒子传输模型。1998年模拟了两个地点的疏浚物处置，一个处置了640，河口内 8 m 深的沉积物为 000 m 3 ，另一处为 230 万米 3 的处置材料，位于岸面 13 m 深。2014 年倾倒场的 19 m 深度模拟考虑在 19 m 水深处处置 1,000.000 m 3 。在对沙滩动物群生态学进行了超过三十年的研究后，与海滩沉积物相关的大量河口腹足动物的出现导致了有关它们在该地区出现的文献搜索。从 1970 年代起，疏浚量不断增加，并使用漏斗式挖泥船沉积到河口和海洋中。CB 的泥浆沉积事件有所增加。疏浚作业后的沉积模式表明自然沉积过程以短暂的方式改变。由南北两个象限的风和风暴产生的洋流为处置场中细粒沉积物的不稳定提供了条件，其流动分量平行并直接流向海岸，而不管波浪的作用如何。流体动力学模型表明，在东北风和南风期间沉积在河口和岸面的沉积物有可能被吹向海滩。疏浚事件后数百万生物的大量沉积不是自然过程，而是疏浚活动的迹象。疏浚可能是环境影响的重要组成部分，因为自然堆积过程在短时间内被细颗粒沉积物的强烈脉冲增强，有利于更频繁的沉积，因为历史和当前的处置地点都不合适。