{"title":"下部平坦平台上沙滩坡度的半经验公式","authors":"Ivana M. Mingo , Laurent Lacaze , Rafael Almar","doi":"10.1016/j.coastaleng.2024.104506","DOIUrl":null,"url":null,"abstract":"<div><p>The beach slope <span><math><mi>β</mi></math></span> is a key component characterizing the coastal response to wave forcing. Here we investigate the rapid adaptation of the upper beach slope to a given wave forcing, for the case of a lower flat platform. Such types of morphology are found on coral and rocky reef beaches and low tide terrace environments. The influence of the lower platform on this rapid equilibrium beach state is shown to be significant depending on the breaking wave regime. In particular, the width of the platform and its water level can affect the wave dissipation along the inner surf and thus the wave structure entering the swash. This paper provides a classification of the beach slope equilibrium values as a function of the Dean number on a short time scale (individual wave action), based on both offshore and swash wave conditions. A decreasing trend of the beach slope with increasing offshore Dean number (<span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) is found for <span><math><mrow><msub><mrow><mi>Ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≲</mo><mn>2</mn><mo>.</mo><mn>7</mn></mrow></math></span>. For <span><math><mrow><msub><mrow><mi>Ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≳</mo><mn>2</mn><mo>.</mo><mn>7</mn></mrow></math></span> it is observed that the beach slope gradient is strongly controlled by the surf zone dissipation and it becomes necessary to define the swash Dean number (<span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>s</mi><mi>w</mi></mrow></msub></math></span>) to classify the slope. Finally, a semi-empirical formula for the beach slope evolution in the case of a low tide platform is introduced and tested on two natural low-tide terrace beaches.</p></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":null,"pages":null},"PeriodicalIF":4.2000,"publicationDate":"2024-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0378383924000541/pdfft?md5=8a7a8a3ab73bb5f5acfb422069300f3f&pid=1-s2.0-S0378383924000541-main.pdf","citationCount":"0","resultStr":"{\"title\":\"A semi-empirical formula of beach slope on flat lower platforms\",\"authors\":\"Ivana M. Mingo , Laurent Lacaze , Rafael Almar\",\"doi\":\"10.1016/j.coastaleng.2024.104506\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>The beach slope <span><math><mi>β</mi></math></span> is a key component characterizing the coastal response to wave forcing. Here we investigate the rapid adaptation of the upper beach slope to a given wave forcing, for the case of a lower flat platform. Such types of morphology are found on coral and rocky reef beaches and low tide terrace environments. The influence of the lower platform on this rapid equilibrium beach state is shown to be significant depending on the breaking wave regime. In particular, the width of the platform and its water level can affect the wave dissipation along the inner surf and thus the wave structure entering the swash. This paper provides a classification of the beach slope equilibrium values as a function of the Dean number on a short time scale (individual wave action), based on both offshore and swash wave conditions. A decreasing trend of the beach slope with increasing offshore Dean number (<span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>) is found for <span><math><mrow><msub><mrow><mi>Ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≲</mo><mn>2</mn><mo>.</mo><mn>7</mn></mrow></math></span>. For <span><math><mrow><msub><mrow><mi>Ω</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>≳</mo><mn>2</mn><mo>.</mo><mn>7</mn></mrow></math></span> it is observed that the beach slope gradient is strongly controlled by the surf zone dissipation and it becomes necessary to define the swash Dean number (<span><math><msub><mrow><mi>Ω</mi></mrow><mrow><mi>s</mi><mi>w</mi></mrow></msub></math></span>) to classify the slope. Finally, a semi-empirical formula for the beach slope evolution in the case of a low tide platform is introduced and tested on two natural low-tide terrace beaches.</p></div>\",\"PeriodicalId\":50996,\"journal\":{\"name\":\"Coastal Engineering\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":4.2000,\"publicationDate\":\"2024-03-18\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S0378383924000541/pdfft?md5=8a7a8a3ab73bb5f5acfb422069300f3f&pid=1-s2.0-S0378383924000541-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Coastal Engineering\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0378383924000541\",\"RegionNum\":2,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"ENGINEERING, CIVIL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Coastal Engineering","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0378383924000541","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, CIVIL","Score":null,"Total":0}
A semi-empirical formula of beach slope on flat lower platforms
The beach slope is a key component characterizing the coastal response to wave forcing. Here we investigate the rapid adaptation of the upper beach slope to a given wave forcing, for the case of a lower flat platform. Such types of morphology are found on coral and rocky reef beaches and low tide terrace environments. The influence of the lower platform on this rapid equilibrium beach state is shown to be significant depending on the breaking wave regime. In particular, the width of the platform and its water level can affect the wave dissipation along the inner surf and thus the wave structure entering the swash. This paper provides a classification of the beach slope equilibrium values as a function of the Dean number on a short time scale (individual wave action), based on both offshore and swash wave conditions. A decreasing trend of the beach slope with increasing offshore Dean number () is found for . For it is observed that the beach slope gradient is strongly controlled by the surf zone dissipation and it becomes necessary to define the swash Dean number () to classify the slope. Finally, a semi-empirical formula for the beach slope evolution in the case of a low tide platform is introduced and tested on two natural low-tide terrace beaches.
期刊介绍:
Coastal Engineering is an international medium for coastal engineers and scientists. Combining practical applications with modern technological and scientific approaches, such as mathematical and numerical modelling, laboratory and field observations and experiments, it publishes fundamental studies as well as case studies on the following aspects of coastal, harbour and offshore engineering: waves, currents and sediment transport; coastal, estuarine and offshore morphology; technical and functional design of coastal and harbour structures; morphological and environmental impact of coastal, harbour and offshore structures.