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Dynamics of Rip currents and Implications for Beach Safety (DRIBS)

离岸流动态及其对海滩安全的影响 (DRIBS)

基本信息

批准号：
NE/H004262/1
负责人：
Gerhard Masselink
金额：
$ 51.95万
依托单位：
Plymouth University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH004262%2F1
关键词：
Dynamics Rip currents Implications Beach

项目摘要

Rip currents are strong and narrow currents in the surf zone that extend seaward of the breaking waves and return water seaward that has been transported into the surf zone by breaking waves. Rip currents are found on high-wave beaches with bars with the rips cutting through the bars in the form of distinct channels. Rip currents can be very strong with flow velocities of 1-2 m/s and are the main hazard to surf zone water users. According to lifeguard records, over 68% of incidents ('rescues') on UK beaches can be attributed to rip currents. A similar percentage is reported from Australia and the USA and, in Florida alone, over 100 people drown each year due to rip currents. Rip currents not only transport people out to sea, but also other material, such as sediment, plankton, nutrients and pollutants. Rip currents are therefore also important for beach erosion and surf zone water quality. The importance of rip currents for beach safety is well recognised by coastal scientists and lifeguards, but we do not fully understand what controls their flow strength and pattern. Our understanding is particularly poor for rip currents on beaches with a large tide range. On some beaches, strong rips cut through bars and sweep swimmers out to sea, whereas on other beaches the rip current develops a large circulating eddy within the surf zone. The risks posed to surf zone water users, and the potential for beach erosion and surf zone flushing, will depend strongly on the type of rip circulation. We believe that rip currents are strongest when all wave breaking occurs on the bar and none of the waves break in the rip channel. We hypothesise that under such conditions the rip generation mechanism is maximised and this depends on wave conditions, tide and bar morphology. All three factors vary over time and even subtle changes in any of them may have significant repercussions for the rip circulation. The overall aim of this project, Dynamics of Rip currents and Implications for Beach Safety (DRIBS), is to test this idea by measuring rip currents under a variety of wave, tide and beach conditions, and complementing the data analysis with computer modelling. We will conduct a 6-week field campaign on two high-wave, large-tidal beaches along the north Cornish coast where mass rescue events of upwards of 150 people per beach have required simultaneous rescue due to rip currents. During each of these campaigns, we will install several instruments in the surf zone that will measure waves, tides and rip currents at fixed locations. In addition, we will use a large number of specialist drifters that measure the complete rip current pattern. The drifters will be released in the surf zone and will move according to the nearshore current pattern. Their location will be continuously monitored (using GPS) and the data from the drifters will provide useful information not only on the strength of the rip current, but also on the type of flow pattern. The drifters are designed to behave like human beings and their movement therefore mimics that of passive bathers. The information collected during the field campaigns will be used to develop a computer model that is able to predict the rip flow pattern for any given wave, tide and beach condition. We will then use this model to develop tools that can be used by lifeguards to determine the rip current risk and develop strategies to deal with this risk. This research project involves the Royal National Lifeboat Institution (RNLI) as a Partner and the RNLI will be involved during all stages of the work. The partnership will be mutually beneficial: the RNLI will help us with the field measurements by making available their dedicated staff and facilities, and we will pass on the research findings to the RNLI via workshops, lectures, leaflets and other types of publications. More importantly, the research findings will be incorporated into the RNLI's risk assessment procedures and resource management tools.

裂流是碎波带中的强而窄的流，其向碎波的海方向延伸，并将已被碎波输送到碎波带中的水向海方向返回。裂流出现在有沙洲的高浪海滩上，裂流以独特的通道形式切割沙洲。裂流可能非常强，流速为1-2 m/s，是碎波区用水者的主要危险。根据救生员的记录，英国海滩上超过68%的事件（“救援”）可以归因于离岸流。澳大利亚和美国也报告了类似的比例，仅在佛罗里达，每年就有100多人因离岸流而溺水。离岸流不仅把人带到海里，也把其他物质，如沉积物、浮游生物、营养物质和污染物带到海里。因此，离岸流对海滩侵蚀和碎波带水质也很重要。离岸流对海滩安全的重要性得到了海岸科学家和救生员的充分认可，但我们并不完全了解是什么控制了它们的流动强度和模式。我们对大潮差海滩上的裂流的了解特别少。在一些海滩上，强烈的撕裂切断了酒吧，并将游泳者卷到海里，而在其他海滩上，撕裂电流在碎波区内形成了一个大的循环涡流。对碎波带用水者造成的风险，以及海滩侵蚀和碎波带冲刷的可能性，将在很大程度上取决于撕裂环流的类型。我们认为，当所有的波浪破碎发生在酒吧和没有一个波浪破碎在裂槽中时，裂流是最强的。我们假设，在这种条件下，撕裂生成机制是最大化，这取决于波浪条件，潮汐和酒吧形态。所有这三个因素都随时间而变化，即使其中任何一个的细微变化都可能对撕裂环流产生重大影响。该项目的总体目标，激流动力学和海滩安全的影响（DRIBS），是通过测量各种波浪，潮汐和海滩条件下的激流，并补充计算机建模的数据分析来测试这一想法。我们将在康沃尔语北部海岸沿着的两个高波浪、大潮汐海滩上进行为期6周的实地活动，由于撕裂流，每个海滩的大规模救援事件超过150人，需要同时进行救援。在每一次活动中，我们将在碎波区安装几台仪器，在固定位置测量波浪、潮汐和离岸流。此外，我们将使用大量的专业漂流测量完整的撕裂电流模式。漂流物将被释放在碎波区，并将根据近岸流模式移动。将（使用全球定位系统）不断监测漂流物的位置，漂流物的数据不仅将提供关于离岸流强度的有用信息，而且还将提供关于流动模式类型的有用信息。漂流者的行为被设计成像人类一样，因此他们的运动模仿了被动的游泳者。在实地活动中收集的信息将用于开发一个计算机模型，该模型能够预测任何给定波浪、潮汐和海滩条件下的裂流模式。然后，我们将使用这个模型来开发救生员可以使用的工具，以确定撕裂电流的风险，并制定策略来应对这种风险。该研究项目涉及皇家国家救生艇研究所（RNLI）作为合作伙伴，RNLI将参与所有阶段的工作。这种伙伴关系将是互惠互利的：RNLI将通过提供专门的工作人员和设施来帮助我们进行实地测量，我们将通过研讨会，讲座，传单和其他类型的出版物将研究结果传递给RNLI。更重要的是，研究结果将纳入RNLI的风险评估程序和资源管理工具。