Rip Current Occurrence Research Articles

A wave-resolving modeling study of rip current variability, rip hazard, and swimmer escape strategies on an embayed beach

Abstract. Drownings due to rip currents are a major threat to beach safety. In this study a high-resolution Boussinesq model with a modified wave-resolving Lagrangian tracking module has been applied to a 2 km long embayed beach, Dadonghai of Sanya, Hainan Island, with the purpose of studying rip current variability, real-time rip hazard identification, and the optimal swimmer escape strategies. The beach stage evolves periodically at the study site and plays an important role in the long-term modulation of the occurrence and strength of rip currents according to the modeling. A series of tests are designed and confirm that rip current strength is closely related to wave properties and tidal levels. Spectral analysis of output time series at specific points shows that the modeled rip currents fluctuate on the orders of 1 and 10 min, which suggests the effects of wave-group-forced infragravity (IG) and very-low-frequency (VLF) motions. Rip hazard levels are defined by combining rip strength and its duration. An attempt to use the GPU-accelerated FUNWAVE-TVD (Total Variation Diminishing version of the Fully Nonlinear Boussinesq Wave Model) embedded with the spectral wave model WAM6-GPU (GPU version of the third-generation spectral wave model WAM Cycle 6) exhibits its capability to evaluate rip hazard levels in real time. One of the differences of the present study from previous works is that the random, wave-resolving tracking of virtual swimmers is performed with 1 m resolution to study beach safety strategies. The results demonstrate that multiple factors contribute to the survival of swimmers caught in the rip currents, including surf-zone bathymetry, rip strength, fine-scale flow patterns, the bather's position, and swimming ability. For weak-to-moderate rip currents and longshore currents, swim onshore consistently seems to be the most successful strategy across all the scenarios in this study. Higher surf-zone exit rates along Dadonghai beach are not favorable for stay afloat action, which puts swimmers at a higher risk of being expelled to deeper water. The effects of wave randomness of incoming wave trains and assignment of wave-following coefficients on Lagrangian tracking are also discussed.

STUDY OF METHODS FOR DETECTING OCCURANCE OF RIP CURRENT USING IMAGE ANALYSIS

There are from 2,000 to 3,000 rescues every summer at bathing beaches in Japan, and the main cause of drowning accidents is rip currents. To analyze the rip current, a method for visualizing rip currents with average images can be used. However, in case of the investigation over a long period, such as several months, it is necessary to confirm the occurrence of rip currents through thousands of averaged images by human eyes. In this study, we suggested a new method for detecting the occurrence of rip currents automatically by analyzing the pixel values of averaged images. Images for the analysis were created from video data recorded in March and April 2021 by a camera overviewing the study beach located on the west coast of Japan. The accuracy results of this method were 99 percent for the validation dataset and 57 percent for the verification dataset, respectively. When the wave height was 0.5 m and higher for the verification dataset, the accuracy was 75percent. Therefore, it was considered that this method can detect the occurrence of rip currents when the wave height is 0.5 m and higher. As a result of applying this method to the 3-month image data recorded from October to December 2021, it was found that wave steepness was occurring lower under the conditions of rip currents. In conclusion, this method was able to automatically detect the rip currents from the images, and the conditions of waves when the rip currents that occurred could be investigated using this method.

Field observation and numerical analysis of rip currents at Ten-Mile Beach, Hailing Island, China

Rip currents are a type of high-speed cross-shore current that occur in coastal areas. They are one of the deadliest natural hazard that occur along coasts. At Ten-Mile Beach on Hailing Island in Yangjiang, China, there have been a number of drowning accidents, most of which have been investigated to be related to rip currents. In order to investigate the rip current phenomenon at this beach, a 24-day beach observation was conducted from August 7 to August 30, 2021. This field investigation included wave observation in the surf zone, bathymetric measurements, unmanned aerial vehicle (UAV) monitoring, and sediment sampling. During the investigation, the beach state changed successively from barred to low tide terrace rip currents and low tide bar/rip, which are beach types with a high probability of rip current occurrence. Wave height was the main factor controlling the beach state and the occurrence of rip currents. The numerical simulation results of the XBeach model were in good agreement with images taken by UAV, confirming that the rip current hazard estimation model can effectively characterize the rip current hazard level for different beach stages. The results of the study provide a useful reference for beach development management and rip current warning at Ten-Mile Beach.

Rip current occurrences in meso tidal surf zones at a coastal stretch along the central west coast of India

Currents in the surfzone were measured and modeled along a coastal stretch on the central west coast of India. Wave and tide were the primary forcings for the numerical model, which was validated with the measurements. The rip current occurrences concerning the prevailing coastal processes are attempted, and the instances where the rip currents can prevail are identified. The wave height, wave period, wave direction, and water level in the nearshore waters were correlated with the rip current (>0.2 m/s) occurrence. The wave period around 7–8 s and the wave direction between 240° and 275° significantly contributed to the rip currents over the entire study region. Along Sinquerim and Candolim beach stretch, a high prevalence of rip currents is observed for wave heights in the range between 1.4 and 1.6 m. In contrast, in Candolim and Baga beaches, the rip current prevalence is greater for wave heights ranging between 0.4 and 0.7 m. In comparison, the tide level between 0.5 and 1 m was significant along the Sinquerim–Candolim stretch. In contrast, tide levels between 0.75 and 2 m were significant in rip current occurrence for the Calangute and Baga stretch.

Mechanism of Rip Current Generation at Deoksan Beach, South Korea

Chang, S.-Y.; Kim, J.-H.; Lee, H.-S., and Kim, I., 2021. Mechanism of rip current generation at Deoksan Beach, South Korea. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 295–299. Coconut Creek (Florida), ISSN 0749-0208. The coast serves as a buffer by reducing the energy of high waves and also serves as a leisure space for people. The east coast of Gangwon has become popular for its beach and for surfing in summer. Most beaches are sandy, and they have well-developed crescentic bars owing to exposure to high waves. The study site, Deoksan Beach, had an accident in which two college students drowned owing to rip currents at around 5:40 pm on July 13, 2019. The flow velocity and direction of the rip currents were identified using CCTV images at the time of the accident, and the causes of the currents were analyzed using data obtained from five water depths surveys conducted in 2017. At the time of the accident, the significant wave height was 0.6 m, the period was ∼7.5 s, and the wave direction was 54°. The survey results indicated that an environment suitable for rip current generation existed at this site. A numerical model experiment was conducted using the non-hydrostatic Surface Waves till Shore (SWASH) model to reproduce the occurrence of rip currents at the time of the accident, and the flow (surface: 0.38 m/s, average: 0.3 m/s) was found to be on the offshore side of the accident.

Rip currents in the southern Baltic Sea multi-bar nearshore zone

Rip currents in the southern Baltic Sea coastal zone are one of the most incompletely known and least explored hydrodynamic phenomena. As they are rare, discussion on their nature, their contribution to the complex pattern of nearshore currents, and their effect on, inter alia, the seafloor transformations is still on-going. Observations made during this study confirmed the occurrence of rip currents at the southern Baltic Sea shore. During field surveys in 2011–2013, Lagrangian measurements taken using novel GPS-tracked drifters revealed several flow events with features characteristic of rip currents. At the same time, numerical calculations produced a three-dimensional wave-current field in the surf zone. Both the measurements and numerical modelling made it possible to follow the rip current dynamics in the area of study and to compare the rip currents observed with those known from other reflective coasts. In addition, wave action-related and bathymetric conditions conducive to the rip current emergence were identified, and the relationship between the rip current velocity, wave regime and local seafloor morphology was explored. The results confirm the theory of rip currents at dissipative shores emerging at the prevalence of fairly flat long waves. Such conditions are typical at swells, i.e., during storm abatement.

User's Perceptions about Rip Currents and Their Specific Management Approaches at a Densely Occupied Urban Beach

Silva-Cavalcanti, J.S.; Silva, A. R.L; Silva, J.C.P; Araújo, M.C.B; Maragotto, M.G., and Costa, M.F., 2020. User's perceptions abourt rip currents and their specific management approaches at a densely occupied urban beach. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 953-957. Coconut Creek (Florida), ISSN 0749-0208.This research aimed to analyze the beach user`s perceptions about rip currents and their specific management approaches at a densely occupied urban beach. Semi-structured questionnaires (N = 216) inquired beach users about use, rip currents knowledge and other hazards. When the beach user's accepted to respond the inquire, they signed an Informed Consent Form. In the 189 valid interviews, females (68%) go to Pina and Boa Viagem beaches more often than males (32%). The choice of the beach part where the beach user will remain was based on easy access (75%), security (13%) and < 6% for fashionable sites, beverages and snacks availability. Rip currents identification is poor, and many are unaware of the meaning of beach safety flags (34%). Around 35% of beach users affirmed not knowing the meaning of the red flags. According to beach users, lifeguards designate areas that are safe for bathing using a pair of red flags. So, they believed that this flag means the area is patrolled by lifeguards, and therefore safer. Other beach users associated red flags to shark attacks (66%). Beach users respondents were asked which area they thought was the safest place to swim and they selected rip channels as the safest place to swim. Beach users declared they know how to swim (71%), however with a swimming ability of < 25 m (84,5%). Information about rip currents is an essential component in developing interventions aimed at reducing the risk of drowning events. Specific management approaches (e.g. red flags) need to focus on debunking rip current myths, to improve understanding of safe swimming areas. The use of flags to indicate the occurrence of rip currents was a partially effective measure of beach management aiming at the prevention of drowning or shark attacks due to beach user's reduced knowledge about rip currents in general and flags meaning.

Rip current occurrence probability at selected recreational beaches along Pahang coastline

Purpose Pahang beaches draw more than thousand visitors throughout the year. From the year 2006 to 2018, more than 30 drowning and near-drowning cases were recorded mainly from rip currents. Rip currents are defined as unexpected currents that carried beachgoers away to seaward direction more than approximately 50 m from shore. The prediction of rip current development is very important for the protection of human life. This study aims to conduct preliminary survey and field works to identify rip current hazards. Design/methodology/approach The output would be an early warning preventative mitigation to public in Pahang. Beach state model, dimensionless fall velocity, littoral environment observation and relative tidal range were recorded for five recreational beaches during two different months (March and April 2018). The morphodynamic parameters such sediment fall velocity, sediment grain size and beach slope are then analysed using software PROFILER. Classification of risks was done based on beach morphodynamic model. The morphodynamics are classified as low tide bar rip, barred and low tide terrace associated with rip current, bar dissipative, reflective, non-bar dissipative, low tide terrace and ultra-dissipative. Findings Result shows three out of five recreational beaches may develop high-risk rip currents. During the first month of the survey, Batu Hitam (BH) was recorded the only one recreational beach that may develop high-risk rip current followed by Teluk Cempedak (TC) and Kempadang (KEM) as middle-risk rip current beaches, while Balok (BA) and Sepat (SEP) as low-risk rip current beaches. Different during second month of the survey, BA, BH and SEP were recorded as high-risk rip current beaches while TC and KEM as low-risk rip current beaches. Originality/value The results are consistent with beach incidents (drowning and near-drowning) reported.

Research on monitoring of ripcurrent occurrence based on cooperation of multiple drones

Research on monitoring of ripcurrent occurrence based on cooperation of multiple drones

Morphometric and sediment analysis of beach cusp in correlation to rip currents: a case study from tropical coast, West coast of India

The presence of rhythmic beach cusps in foreshore regions are of persistent research interest to coastal researchers, engineers with respect to their formation in beaches. Morphometric and sediment analysis were used to study beach cusp morphology at Vengurla beach, a gentle slope beach characterized by medium sand. The cusp dimensions such as spacing, elevation, amplitude and depth were measured for detailed analysis. The distinctive sediment characteristics between the horn and the bays of the cusp are different and cusp measurements show a high level of irregularity. Horns and bays have medium sand, but sorting is varying. Sorting variations clearly demonstrated the difference in energy condition between horns and bay. Negative skewness of few horn samples has been correlated with erosional trend. Based on the grain size analysis result, it was observed that Vengurla beach cusps follow the regular grain size distribution pattern. Additionally, the low-intensity rip currents were also noticed in the study area. The rate of occurrence and strength of rip currents are decided by the nearshore bathymetry and play an imperative role in rip current formation. The present study is based upon the field measurements along Vengurla coast and contributes to morphometric analysis of beach cusps. Regarding beach cusps, there are no documented databases along the Indian coast. Understanding the beach cusp formation and its seasonal changes along the beaches will be useful for effective coastal management.

Improving the Performance of Rip Current Forecasting Index with a Focus on Haeundae Beach, Korea

ABSTRACT Lee, J.; Kim, I., and Lee, J.L., 2018. Improving the performance of rip current forecasting index with a focused on Haeundae Beach, Korea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1556–1560. Coconut Creek (Florida), ISSN 0749-0208. Rip currents can potentially drag swimmers into deep water, beyond seaward sand bars, and hence pose great threat to beach visitors worldwide. The primary aim of this study was to develop a method for improving the performance of rip current forecasting indices to more effectively, demonstrate a rip current warning level. The previous rip current forecasting index was established with four predictive levels: notice, watch, warning, and danger. The new index is based on a numerical model, using wave and wind data as well as forecast information. Through this study, standardization of rip current occurrence levels has ...

Rip current evidence by hydrodynamic simulations, bathymetric surveys and UAV observation

Abstract. The prediction of the formation, spacing and location of rip currents is a scientific challenge that can be achieved by means of different complementary methods. In this paper the analysis of numerical and experimental data, including RPAS (remotely piloted aircraft systems) observations, allowed us to detect the presence of rip currents and rip channels at the mouth of Sele River, in the Gulf of Salerno, southern Italy. The dataset used to analyze these phenomena consisted of two different bathymetric surveys, a detailed sediment analysis and a set of high-resolution wave numerical simulations, completed with Google EarthTM images and RPAS observations. The grain size trend analysis and the numerical simulations allowed us to identify the rip current occurrence, forced by topographically constrained channels incised on the seabed, which were compared with observations.

Nearshore Current Pattern and Rip Current Occurrence at Jungmun Beach, Jeju by Numerical Computation

A nearshore current or a wave-induced current is an important phenomenon in a nearshore zone, which is composed of longshore, cross-shore, and rip currents. The nearshore current is closely related to the occurrence of coastal accidents by beachgoers. A considerable number of coastal accidents by beachgoers involving the rip current have been reported at Jungmun Beach. However, in studies and observations of the nearshore current of Jungmun Beach, understanding of the rip current pattern remains unclear. In this study, a scientific approach is taken to understand the nearshore current and the rip current patterns at Jungmun Beach by numerical computation for year of 2015. From results of numerical computation, the occurrence and spatial characteristics of the rip current, and the similarities between the rip current and incident wave conditions are analyzed. The primary results of this study reveal that the rip currents are frequently generated at Jungmun Beach, especially in the western parts of the beach, and that the rip currents often occur with a wave breaking height of around 0.5 ~ 0.7 m, a wave period of around 6 ~ 8 seconds, and a breaking angle of around 0 ~ 15 degrees.

Numerical Study of Rip Current Generation at Daecheon Beach, West Coast of Korea

ABSTRACT Yoon, J.-J., 2017. Numerical study of rip current generation at Daecheon Beach, west coast of Korea. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 259–263. Coconut Creek (Florida), ISSN 0749-0208. Daecheon Beach in Boryeong, Korea, is one of the most popular places on the west coast of Korea. The world famous “Mud Festival” attracts visitors in summer and this beach has many tourists throughout the year. However, the irregular occurrence of rip currents threatens swimmers during every summer season. Two people were swept away by fast moving rip currents in August 2010, and could not be rescued. To investigate the dominant mechanism of rip currents in this region, a numerical simulation was carried out using the non-hydrostatic model Surface WAves till SHore (SWASH), with observed wave and topographical data. In this paper, the applicability of SWASH for modeling wave tra...

Field Observation and Numerical Modelling of Rip Currents within a Pocket Beach

ABSTRACT Shin, S.; Nam, J.; Son, S.; Kim, I.H., and Jung, T.-H., 2017. Field observation and numerical modelling of rip currents within a pocket beach. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 229–233. Coconut Creek (Florida), ISSN 0749-0208. Understanding the occurrence mechanism of rip currents are very important in terms of the sediment transport and the water safety issues. In order to investigate the rip current occurrence mechanism, field observations were carried out at Chunjin beach and a numerical model was employed to simulate rip currents by using the field observation data. The collected data set includes the beach topography, bottom bathymetries, shoreline, sand sample, and incident waves for each season. The field observation data showed the spatiotemporal variations of shoreline and sand bars. The results also showed that the rip currents were generated near t...

Quantitative Behaviour Characteristics Analysis of GPS Buoy in Rip Current Generation

ABSTRACT Song, D.S; Kim, G.Y., and Lee, J.L., 2016. Quantitative behaviour characteristics analysis of GPS buoy in rip current generation. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1242 - 1246. Coconut Creek (Florida), ISSN 0749-0208. GPS buoys have been used to acquire sea level change data, current measurements and other oceanic variables in sea for the purposes of vertical datum determination, tide correction, radar altimeter calibration, ocean environment and marine pollution monitoring. The occurrence of rip currents in the Haeundae beach, which is one of the most famous beaches in South Korea, has been threatening beach-goer security in summer season annually. Therefore, we adopted a GPS buoy system for an experiment which is to investigate rip current velocity; it is sporadic and may quickly upsurge within minutes due to larger arrivi...

The Application of a Rip Current Warning Decision-Process System, Haeundae Beach, South Korea

ABSTRACT Lee, J.; Cho, W.C., and Lee, J.L., 2016. The Application of a Rip Current Warning Decision-Process System, Haeundae Beach, South Korea. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1167 - 1171. Coconut Creek (Florida), ISSN 0749-0208. Rip currents have the potential to pull swimmers into deep water, beyond offshore sand bars, posing a significant danger to beach goers worldwide. At Haeundae Beach in Busan, a south eastern region of South Korea, many rip current events have recently occurred, resulting in a number of people requiring rescue from these fast moving, seaward currents in 2014. The main objective of this study was to provide a warning decision-process for the occurrence of rip currents, to aid in the protection of human life in the areas where these rip currents occur. The rip current warning decision-process system develope...

Dynamic Modelling of Rip Currents for Swimmer Safety on a Wind-Sea–Dominated Mesotidal Beach

ABSTRACT Sembiring, L.; van Dongeren, A.; Winter, G., and Roelvink, D., 2016. Dynamic modelling of rip currents for swimmer safety on a wind-sea–dominated mesotidal beach. This study applied the process-based model XBeach to predict bathymetrically controlled rip current flow occurrence, velocities and duration in the wind-sea–dominated environment of Egmond aan Zee, The Netherlands. The model is validated against data obtained during a 5-day field experiment with GPS-equipped floating drifters. Numerical model results show good agreement with data and simulate flow patterns that resemble the offshore flow through the rip channel and subsequent alongshore drift of the drifters. The average relative error of the drifter position is 0.15 and 0.19 for the cross-shore and the alongshore position, respectively. Results from the numerical experiments suggest that the rip current intensity is tidally modulated. For the period of analysis, the rips are initiated approximately 5 hours before low tide, reaching a m...

Rip Current Research Using a CCTV Image Analysis Including Swimmer Detecting Techniques at Haeundae Beach, Korea

Hwang, J.S.; Yun, H.S.; Suh, Y.C.; Lee, J., and Kang, S.C., 2014. Rip current research using a CCTV image analysis including swimmer detecting techniques at Haeundae Beach, Korea.In this study, a rip current analysis method using images from a CCTV installed on a beach was investigated. A method that automatically calculates the absolute coordinates of a swimmer captured via CCTV by combining image recognition technology and single photo-based photogrammetry was developed, and a method by which the analysis of many calculated absolute coordinates could be used for the monitoring of rip current occurrence, studies on rip current occurrence trend, and the measurement of stream velocity at the surface of a rip current was suggested. The image captured during the occurrence of a rip current at Haeundae Beach was analyzed as an example. Based on this analysis, it was found that the method suggested in this study was appropriate for the research and monitoring of a rip current.

Numerical Studies on Rip Current Control Using Scene-friendly Structures at Haeundae Beach, Korea

ABSTRACT Lee, W.D.; Shin, S.W.; Jeong, Y.M., and Hur, D.S., 2014. Numerical studies on rip current control using scene-friendly structures at Haeundae Beach, Korea. The sporadically occurring rip currents put swimmers in risk during the season of every summer vacation. It is known that the rip current generation is affected by the characteristics of incident waves and bottom topography but the mechanism of the rip current occurrence is still not clear. In order to understand the mechanism of the rip current and to establish countermeasures, 3D numerical simulation was performed based on the realistic bathymetry of Haeundae Beach by using LES-WASS-3D. The numerical simulation results showed that the wave heights vary parallel to the shore line by inequality of bottom bathymetry (submerged shoal and rocks) and this wave height variation induces the water level difference. The model results also showed that the rip currents were generated through the region of relatively deep water and low water level that i...