Variability in infragravity wave processes during estuary artificial entrance openings,Earth Surface Processes and Landforms

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Variability in infragravity wave processes during estuary artificial entrance openings
Earth Surface Processes and Landforms ( IF 2.8 ) Pub Date : 2020-08-06 , DOI: 10.1002/esp.4974
Sarah L. McSweeney ₁ , Justin C. Stout _{1,

2} , David M. Kennedy ₁

Affiliation

Intermittently open/closed estuaries (IOCE) are wave‐dominated estuaries with entrances that temporarily close to the ocean. Wave–current interactions play a major role in estuary entrance morphodynamics and influence the degree of energy transfer from the ocean into the lagoon. This study utilizes artificial entrance openings of multiple ICOE in Victoria, Australia, to capture continuous hydrodynamic and geomorphic data throughout the opening cycle. We illustrate that water level oscillations in the infragravity (IG) band) are present in the basin during open entrance conditions. IG waves were observed to propagate up to 1.8 km upstream of the mouth while the entrance was open. Our work identifies that changes in cross‐sectional area, bed depth at the berm position, and offshore wave height control the magnitude of IG waves within the estuary basin. IG wave magnitude is also tidally modulated and increases with high tides when the nearshore water level is higher. Late during the drainage phase, waves were observed to track the margins of the channel, away from the thalweg, and reach the basin. IG wave energy was highest immediately after the basin had ceased draining and while channel dimensions at the mouth were within 10% of their maximum value. As the entrance aggrades, IG wave magnitude decreases in the absence of energetic offshore wave conditions. We relate the changes in IG wave magnitude and frequency to a six‐stage conceptual model of the opening–closure sequence. Within the basin, IG wave energy, height and frequency were also consistently highest closer to the mouth and decreased with distance upstream. Our findings indicate that water level oscillations in the IG band are a persistent feature in IOCE and may be the norm rather than the exception in these systems. As IG waves were captured serendipitously as part of a larger field campaign, future work will focus on instrumenting IOCE to gain high‐resolution data to quantify IG wave processes during entrance openings. © 2020 John Wiley & Sons, Ltd.

中文翻译：

河口人工入口开口处重力波过程的变化

间歇性开/关河口（IOCE）是波浪主导的河口，其入口暂时靠近海洋。波流相互作用在河口入口形态动力学中起主要作用，并影响能量从海洋到泻湖的转移程度。这项研究利用了澳大利亚维多利亚州多个ICOE的人工入口，以捕获整个开放周期中连续的水动力和地貌数据。我们说明，在开放式入口条件下，盆地中会出现超重力（IG）带中的水位振荡。当入口打开时，观察到IG波在嘴上游传播了1.8 km。我们的工作可以确定横截面的变化，在护堤位置的床深，海上波浪高度控制着河口盆地内中空浪的强度。IG波的大小也经过潮汐调制，并且当近岸水位较高时，潮汐会增加。在排水阶段的后期，观察到波浪来追踪通道的边缘，远离海藻，到达盆地。盆地停止排水后，在入口处的通道尺寸在其最大值的10％以内时，IG波能量立即最高。随着入口的渐进，在没有高能离岸波浪条件的情况下，IG波强度会降低。我们将IG波幅值和频率的变化与打开-关闭序列的六阶段概念模型相关联。在盆地内，中波能量，高度和频率在靠近嘴处也始终最高，并随着上游距离而降低。我们的发现表明，IG波段中的水位振荡是IOCE的持久特征，在这些系统中可能是正常现象，而不是例外情况。由于在大型野战中偶然捕获了IG波，未来的工作将重点放在IOCE仪器上，以获取高分辨率数据以量化入口开口期间的IG波过程。©2020 John Wiley＆Sons，Ltd. 未来的工作将重点放在仪器IOCE上，以获取高分辨率数据以量化入口开口期间的IG波过程。©2020 John Wiley＆Sons，Ltd. 未来的工作将重点放在仪器IOCE上，以获取高分辨率数据以量化入口开口期间的IG波过程。©2020 John Wiley＆Sons，Ltd.

更新日期：2020-08-06

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