Abstract
Rip currents are strong water channels flowing away from the shoreline. They can occur on any shore with breaking waves. Rip currents play a significant role in changing the topography of shallow water regions by transporting large amounts of bed material offshore. Moreover, they pose a significant danger for people living in nearshore zones and surfers and cause hundreds of deaths annually worldwide. Therefore, rip current generation characteristics have been investigated to prevent casualties. In this study, a GPS drifter survey was chosen as the investigation method; however, a few drawbacks were discovered, such as low accuracy due to the GPS drifter becoming trapped in the surf zone. Therefore, drones and dyes were used to overcome the drawbacks of drifter methods. The results of dye tracking and the 3D wave-induced current numerical simulation were compared; the velocity and formation of the rip current were found to be relatively similar. With the technological advancements and invention of new survey equipment, the survey techniques also evolve, and this paper shows that the disadvantages of the GPS-based Lagrangian method can be overcome using a dye-mounted drone, which observes the rip current easily and accurately.
Highlights
Rip currents are fast seaward water currents that flow in a narrow channel from the surf zone [1]
Conclusions the incident wave height of the numerical simulation was used as input data with the average value of the significant wave height measured at 2-h intervals
The result of the orthometric correction of the dye observation images obtained using the drone demonstrated a higher accuracy than the GPS drifter results because they were measured without any limitations that prevent going beyond the surf zone, unlike that in the case of buoys or drifters
Summary
Rip currents are fast seaward water currents that flow in a narrow channel from the surf zone [1]. TThhee bathymetric informaattiioonn was used in the nnumerical simulation for oobtaining basic data to identify and predict the frequent rip current occurrence locations, which are called rip current hot spots in this study. WWaavvee-inindduucceeddccuurrreenntstsccaannbbeeddeessccrribibeedduussininggttwwooeeqquuaattioionnssttoorreepprreesseenntttthheexxaannddyyddiirreeccttiioonnss:: ccoonnttiinnuuiittyyeeqquuaattiioonn((EEqquuaattiioonn((11)))aannddmmootitoionneeqquuaatitoionn(E(Eqquuaatitoionnss(2(2) )anandd(3()3)).).TThheessee eeqquuaattioionnssininccluluddeetthheeeexxteterrnnaallffoorrcceeooffththee22-D-Dmmoonnoolalayyeerrsshhaalloloww-w-waateterreeqquuaatitoionn, ,wwhhicichh ccoommpprrisiseessaawwaavvee-i-nindduucceeddrraaddiaiatitoionnsstrteresssccoommppoonneennt.t. Using the above-mentioned model, the following parameters were used to calculate the wave-induced currents and identify the rip current hot spot: experimental range: 1500 m × 1300 m; the number of grids: 150 × 130 = 19,500; grid size: dx = dy = 10 m. The same method and grid configurations were used to calculate the Atmosphere 2021, 12r,e7a1l9-time wave in the same time zone as that of the rip current observation of the input conditions to compare the numerical simulations from this research with those of Deguchi et al, (2008) [14]. WcuhrirleenctosmuspianrginagGthPeSrdiprifctuerrrdenestiggenneedratotiomnetaesnudreentchiees at Haeundae surf zone circuBlaetaicohn, i[t1w6]a. sTohbeserirpvecdutrhreant tlohnogtshspooret caut rHreanetusnwdearee Bdeeavcehlopweads firdoemnttihfieedwest to the east, through a numgeernicearlatsiinmgusltartoinong riinpccoumrrpeanrtissoinnfrwointht opfrtehveiobueascshtuadt itehse[h1o7t,1s8p].otTleoncaGtiPoSn of the present drifters were dsrtoupdpye.dBuatoythaenrdipdcyuertrreanctkihnogt ospbsoetrsvaantidontrsawckeerde tthoeannpaelyrzfoermtheedriapt cthuerrpernetdicted hot spot. generation pattFeirgnu, rienc6lushdoinwgstthheeahvoetrsapgoetfplorwedvicetlioocnitpyo, imntasxoimbtuaimneidnsutsainntganriepoucusrfrleonwt mveo-del verification locity, and direwctiitohn.thSeimcuurltraennetooubssleyr,vtehde pbarethvyiomuestlyricmteonptoiognraepdhdyy. eTthreaclkoicnagtiomneothfothdewhaost spot obtained using this numerical model was similar to that obtained in a previous study by Deguchi et al [14]; the observations were made at the same location
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