Daily timescale analysis of sediment transport and topographic changes on a mesotidal sandy beach under low to moderate wave conditions

IF 2.6 3区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY
Isaac Rodríguez-Padilla , Ismael Mariño-Tapia , Amaia Ruiz de Alegría-Arzaburu
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引用次数: 0

Abstract

Understanding sediment transport processes on natural sandy beaches is essential for gaining insights into beach recovery and making effective coastal management decisions. This study examines surfzone sediment transport rates related to beachface morphological variations on an embayed mesotidal sandy beach located on the northwestern coast of the Baja California Peninsula in Mexico. Data were collected during a week-long field experiment conducted in June 2016 under low-to-moderate wave energy conditions (Hs=0.41.3m). Daily topographical surveys and continuous measurements of near-bottom suspended sediment fluxes were conducted alongside the application of an extended energetics-based model that accounted for velocity and acceleration skewness. Results reveal contrasting accretionary and erosive patterns in the inner surfzone, along with consistent sediment deposition in the swash zone throughout the study period. Onshore sediment transport is found to be related to short-period calm wave conditions (Hs<0.7 m; Tp<10 s) and a weak undertow (<0.2 ms−1). Alongshore nonuniform wave breaking, influenced by irregular bathymetry and moderate-energetic oblique waves from the northwest, contributes to an alongshore gradient in sediment transport rate, leading to erosion in the northern part of the intertidal beach and accretion in the southern part. Suspended sediment flux measurements at 0.2 m above the bed suggest offshore mean transport predominates over oscillatory transport throughout the field experiment. Nevertheless, this observation should be interpreted with caution, as the flux is not vertically integrated across the water column and does not consider fluid acceleration. The model predictions effectively replicate sediment transport rates and consequent volumetric changes (Accuracy = 55–63%; RMSE = 44–69 m3; Bias=2 to −61 m3), although they underestimate observed accretion by a factor of three and overestimate erosion by a factor of two. Overall, this research highlights the complexities of natural sandy beach recovery processes in mesotidal environments and emphasizes the importance of considering both cross-shore and longshore components in sediment transport assessments.

Abstract Image

中低浪条件下潮间带沙滩沉积物迁移和地形变化的日时间尺度分析
了解天然沙滩的沉积物运移过程,对于深入了解沙滩恢复和做出有效的海岸管理决策 至关重要。本研究考察了位于墨西哥下加利福尼亚半岛西北海岸的一个筑堤潮间带沙滩上与滩面形态变化有关的表层沉积物迁移率。数据是在 2016 年 6 月进行的为期一周的实地实验中收集的,实验条件为中低浪能(Hs=0.4-1.3 米)。在进行每日地形勘测和近底悬浮沉积通量连续测量的同时,还应用了基于能量学的扩展模型,该模型考虑了速度和加速度偏度。研究结果表明,在整个研究期间,内冲浪区的吸积和侵蚀模式截然不同,而斜冲区的沉积物沉积则始终如一。研究发现,沿岸沉积物迁移与短周期平静波浪条件(Hs<0.7 m; Tp<10s)和微弱暗流(<0.2 ms-1)有关。受不规则水深和来自西北方向的中等能量斜波的影响,沿岸的不均匀破浪造成了沉积物迁移率的沿岸梯度,导致潮间带海滩北部的侵蚀和南部的增生。海床上方 0.2 米处的悬浮泥沙通量测量结果表明,在整个现场实验过程中,离岸平均运移比振荡运移更占优势。尽管如此,由于通量没有在整个水体中进行垂直整合,也没有考虑流体加速度,因此在解释这一观测结果时应谨慎。模型预测有效地复制了沉积物运移速率和随之而来的体积变化(准确率 = 55-63%;均方根误差 = 44-69 立方米;偏差 =-2 至 -61 立方米),尽管模型预测低估了观测到的增殖量三倍,高估了侵蚀量两倍。总之,这项研究强调了潮间带环境中天然沙滩恢复过程的复杂性,并强调了在沉积物运移评估中同时考虑跨岸和长岸部分的重要性。
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来源期刊
Marine Geology
Marine Geology 地学-地球科学综合
CiteScore
6.10
自引率
6.90%
发文量
175
审稿时长
21.9 weeks
期刊介绍: Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.
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