Isaac Rodríguez-Padilla , Ismael Mariño-Tapia , Amaia Ruiz de Alegría-Arzaburu
{"title":"Daily timescale analysis of sediment transport and topographic changes on a mesotidal sandy beach under low to moderate wave conditions","authors":"Isaac Rodríguez-Padilla , Ismael Mariño-Tapia , Amaia Ruiz de Alegría-Arzaburu","doi":"10.1016/j.margeo.2024.107323","DOIUrl":null,"url":null,"abstract":"<div><p>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 (<span><math><msub><mi>H</mi><mi>s</mi></msub><mo>=</mo><mn>0.4</mn><mo>−</mo><mn>1.3</mn><mspace></mspace><mi>m</mi></math></span>). 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 (<span><math><msub><mi>H</mi><mi>s</mi></msub><mo><</mo><mn>0.7</mn></math></span> m; <span><math><msub><mi>T</mi><mi>p</mi></msub><mo><</mo><mn>10</mn></math></span> s) and a weak undertow (<0.2 ms<sup>−1</sup>). 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–<span><math><mn>63</mn><mo>%</mo></math></span>; RMSE = 44–69 m<sup>3</sup>; <span><math><mtext>Bias</mtext><mo>=</mo><mo>−</mo><mn>2</mn></math></span> to −61 m<sup>3</sup>), 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.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Marine Geology","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0025322724001075","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
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 (). 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 ( m; 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–; RMSE = 44–69 m3; 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.
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.