Abstract. Rip currents are dangerous flows in the surfzone of wave-exposed coasts and can take bathers from the shallows into deeper water. They cause hundreds of drownings globally each year and are the leading cause of all beach lifeguard rescues. In New Zealand, with a population of approx. 5 million people, rip currents typically cause 500–1000 lifeguard rescues each year and are attributed to 53 % of all Surf Life Saving New Zealand rescues. This study aims to identify environmental conditions associated with rip current incidents and develop a simple algorithm for forecasting rip current risk and hazard. A dataset of ~9,000 recorded rip current rescues along with water user head counts made at 58 beaches by lifeguards around the coast of New Zealand between 2001 and 2022 was used to assess rip current risk (parameterised from the total number of incidents) and rip current hazard (parameterised as the likelihood of an individual being in a rip incident) under different wave, tide, and wind conditions. In concurrence with previous findings, most rip incidents in New Zealand were recorded at beaches with intermediate ‘bar-rip’ beach morphology and occurred disproportionately during wave conditions at or above average breaker height with tide level at or below average low tide. Although rip incidents were also recorded at dissipative and reflective beaches lacking in bar-rip morphology, water users were 4 and 24 times more likely, respectively, to be in a rip-related incident at intermediate beaches with bar-rip morphology. A simple, threshold-based algorithm was developed using only breaker height, relative tide level, and a binary bar-rip morphology variable as predictors for use as a national-scale rip forecast across New Zealand. The algorithm achieves a high incident hit rate, capturing 98 % of historic rip incidents across New Zealand, and captures exponentially increasing hazard at each of its five Rip Index levels, with a water user 6 times more likely to be in a rip incident at the highest Rip Index (~1-in-200) compared to the lowest (~1-in-1200). It also conservatively replicates a lifeguard’s perception of rip hazard, with an overall agreement rate of approximately 81 %, indicating it could provide useful forewarnings to the public especially at non-lifeguarded beaches or outside lifeguard patrol hours. To our knowledge, this represents the longest running rip incident data set analysed, and most widely validated rip forecast in the literature to date.

SCOTT, T., RUSSELL, P., MASSELINK, G., WOOLER, A., and SHORT, A., 2007. Beach rescue statistics and their relation to nearshore morphology. and hazards: a case study for southwest England. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 1 - 6. Gold Coast, Australia, ISSN 0749.0208The coasts of Devon and Cornwall in the southwest of England experience some of the most energetic wave conditions (H(s,10%) = 2-3 m) and largest tide ranges MSR = (4.2-8.6 m) in the UK. They are also a popular tourist destination during the summer months with over 10 million visitors per year. The energetic wave/tide conditions pose a considerable physical risk to beach users and 62 beach environments in this region are therefore patrolled by Royal National Lifeboat Institution (RNLI) lifeguards. Beach rescue statistics collected by the RNLI during spring and summer (1 May to 1 October) were analysed to examine and quantify the risk posed by physical beach hazards to beach users. Rip currents were found to be the main hazard and were responsible for 71% of all recorded incidents. The most hazardous beaches were found on the exposed west coast of the study area. Beaches here can be classified as morphodynamically intermediate and are characterized by low-tide tide bar and rip systems, often topographically-constrained by intertidal geology. The rip currents are generally most active around low tide. Beaches in Devon and Cornwall exhibit morphologies that are significantly different from previously studied beaches in Australia due to the combination of high energy surf zones, large tides and variable coastal geology. This work represents a first step towards the generation of standardized beach risk assessments in the UK.

A rip current is a strong, localized current of water which moves along and away from the shore. Recent studies have suggested that drownings due to rip currents are still a major threat to beach safety. Identification of rip currents is important for lifeguards when making decisions on where to designate patrolled areas. The public also require information while deciding where to swim when lifeguards are not on patrol. In the present study we present an artificial intelligence (AI) algorithm that both identifies whether a rip current exists in images/video, and also localizes where that rip current occurs. While there have been some significant advances in AI for rip current detection and localization, there is a lack of research ensuring that an AI algorithm can generalize well to a diverse range of coastal environments and marine conditions. The present study made use of an interpretable AI method, gradient-weighted class-activation maps (Grad-CAM), which is a novel approach for amorphous rip current detection. The training data/images were diverse and encompass rip currents in a wide variety of environmental settings, ensuring model generalization. An open-access aerial catalogue of rip currents were used for model training. Here, the aerial imagery was also augmented by applying a wide variety of randomized image transformations (e.g., perspective, rotational transforms, and additive noise), which dramatically improves model performance through generalization. To account for diverse environmental settings, a synthetically generated training set, containing fog, shadows, and rain, was also added to the rip current images, thus increased the training dataset approximately 10-fold. Interpretable AI has dramatically improved the accuracy of unbounded rip current detection, which can correctly classify and localize rip currents about 89% of the time when validated on independent videos from surf-cameras at oblique angles. The novelty also lies in the ability to capture some shape characteristics of the amorphous rip current structure without the need of a predefined bounding box, therefore enabling the use of remote technology like drones. A comparison with well-established coastal image processing techniques is also presented via a short discussion and easy reference table. The strengths and weaknesses of both methods are highlighted and discussed.

Drowning is a leading cause of unintentional fatalities around the world, yet on beaches is often preventable through public education campaigns and intervention activities from lifeguards. In 2006, the UK beach lifeguarding community approached the Coastal Processes Research Group (CPRG) at University of Plymouth, UK, with a need to better understand the key hazards on UK beaches and how to foresee and manage the associated risks. In some cases there simply was not sufficient scientifically-robust understanding of certain hazards (for example rip currents) available for lifeguard managers to make objective, data-driven decisions on how to manage them. This paper documents the resulting 15-year body of work, and reflects upon the education, outreach, and other research impacts that have been created, and lessons learned along the way. By furthering fundamental coastal processes understanding of such things as beach classification and rip current dynamics, as well as applying science to challenges such as predicting beach life-risk and times of peak bathing hazard, the ongoing collaboration between lifeguards and academics continues to inform beach safety management in a number of countries around the world. Initiating research with clear aims and objectives that are driven by, and developed in conjunction with, the end-user, as opposed to starting with outcomes prescribed to the end-user by academics, has been an important factor in the success (or failure) of these scientific ventures. CPRG's research activities in the field of beach safety has been scientifically rewarding and have achieved significant impacts. We attribute this to: (1) sustained level of high-quality research; (2) continued effort spent on building long-term relationships with end-users; (3) co-creation of dissemination material and tools; (4) acceptance that it takes time and effort to achieve research impact; and (5) critically evaluating and reflecting on the research impacts. Ultimately, the ongoing collaboration has contributed to a 'continuing trend of decline in accidental fatalities around our coastlines', and such collaborations in other parts of the world continue to play a vital role in reducing coastal drowning globally.

Rip currents ("rips") are the leading cause of drowning on surf beaches worldwide. A major contributing factor is that many beachgoers are unable to identify rip currents. Previous research has attempted to quantify beachgoers' rip identification ability using photographs of rip currents without identifying whether this usefully translates into an ability to identify a rip current in situ at the beach. This study is the first to compare beachgoers ability to identify rip currents in photographs and in situ at a beach in New Zealand (Muriwai Beach) where a channel rip current was present. Only 22% of respondents were able to identify the in situ rip current. The highest rates of success were for males (33 %), New Zealand residents (25 %), and local beach users (29 %). Of all respondents who were successful at identifying the rip current in situ, 62% were active surfers/bodyboarders, and 28% were active beach swimmers. Of the respondents who were able to identify a rip current in two photographs, only 34% were able to translate this into a successful in situ rip identification, which suggests that the ability to identify rip currents by beachgoers is worse than reported by previous studies involving photographs. This study highlights the difficulty of successfully identifying a rip current in reality and that photographs are not necessarily a useful means of teaching individuals to identify rip currents. It advocates for the use of more immersive and realistic education strategies, such as the use of virtual reality headsets showing moving imagery (videos) of rip currents in order to improve rip identification ability.

Rip currents are responsible for 67% of all individuals rescued by lifeguards on UK beaches, representing the greatest environmental risk to water users. There are currently no measures of human awareness of rip currents in the UK, and the worldwide research on human behavioural aspects surrounding rip currents is a small emerging research area. In the last few years the physical understanding of rip current behaviour has been much improved by studies using GPS floats. The aim of this study is to discover the key demographic characteristics of beach users caught in rip currents and the spatiotemporal variation in the UK by analysing the Royal National Lifeboat Institutions lifeguard rip current incident data for 2006 to 2011. The results show male teenagers (aged 13-17 years) are the most likely demographic to be involved in a rip incident., In addition, people bodyboarding, and people in non-patrolled areas of the beach are at higher risk. Rip incidents are most common on the popular Atlantic-facing beaches of north Devon and Cornwall where low-tide bar-rip morphology enhances rip current activity, presenting a major hazard to beach users. This study presents a significant insight into rip victim demographics, identifying key target audiences for future awareness campaigns and rip education schemes. It also provides a benchmark for further research into the investigation of why specific demographics are getting caught in rips by understanding the behaviour of these groups.

The role of beach safety management is becoming increasingly important along much of the macro-tidal, high-energy Atlantic coast of England, which experiences mean spring-tidal ranges of 4.1-7.4 m and average significant wave heights of 1.2 m and 2.7 m in summer and winter, respectively. Growing pressures on beach resources due to increasing visitor numbers means an understanding of the nature of hazards Surrounding the recreational beach user is paramount. Rip currents are responsible for 80% of all recorded incidents (2005-2007) along this coast. Most investigations into rip Current dynamics have been reported from micro- and meso-tidal environments and macro-tidal rip systems have rarely been considered. This research assesses the spatio-temporal variability of macro-tidal rip Current systems and their associated hazards along the west coasts of Devon and Cornwall between May and October 2007. Analysis of seasonal morphological and hydrodynamic datasets coupled with detailed lifeguard incident data and daily rip observations have identified some key drivers of recreational rip hazards and 'mass rescue' events on low-tide bar/rip and low-tide terrace and bar/rip beaches; 1) Small long-period swell-waves, that favour development of accretioary rip systems, shoal to the inner transverse bars generating strong alongshore variations in wave breaking and enhancing rip current activity: 2) Well developed, phase-offset low- and mid-tide bar/rip morphologies lead to the generation of active rip systems during low- and mid-tidal stages; 3) Large (spring) tidal ranges expose low-tide bar/rip systems, activating rip currents and increasing tidal cut-off potential and the rate-of-change of alongshore rip location through low- and mid-tide. Low-tide times during spring tides coincide with lifeguard patrol hours and hence times of high beach usage.

In a coastal region where there are large pressures on the beach resources through recreational usage, understanding the levels and characteristics of risk to the beach user is paramount. A morphodynamic evaluation of beaches in the high-energy, macro-tidal southwest of England was made between July 2006 and February 2008. Levels of physical beach hazards presented to the beach user, both spatially and temporally, by waves, tides and surf-zone currents were assessed and calibrated against lifeguard rescue and usage data. Large seasonal variations in wave energy lead to significant annual morphodynamic transition of the popular west coast beaches from a erosive planar beach face with linear shore parallel bars in winter to a highly three dimensional accretionary system in spring/summer with pronounced low-tide bar/rip systems and enhanced mid-tide bar morphologies. In many locations this general transition is modified through sediment supply, geological constriction and freshwater drainage. This annual transition drives temporal variations in beach hazard through (1) the temporal variability morphology (especially rip currents, the cause of 68% of all incidents during 20052007); and (2) large tidal excursion during spring tide periods exposing low tide rip systems increasing the rate of change of the temporal hazard signature. Periods of high morphologically driven beach hazard coincide with seasonal peaks in beach user numbers, increasing recreational beach risk.