applied sciences Article A Hydraulic Experimental Study of a Movable Barrier on a Revetment to Block Wave Overtopping Byeong Wook Lee, Jihye Seo, Woo-Sun Park and Deokhee Won * Korea Institute of Ocean Science and Technology (KIOST), 385 Haeyang-ro, Yeongdo-gu, Busan 49111, Korea; [email protected] (B.W.L.); [email protected] (J.S.); [email protected] (W.-S.P.) * Correspondence: [email protected]; Tel.: +82-51-664-3565 Received: 8 November 2019; Accepted: 19 December 2019; Published: 20 December 2019 Abstract: This paper presents a design for a movable barrier on the revetment of the Haeundae Marine City in Busan, the Korea. This movable barrier was developed to use as a tourist deck in a normal state and to block wave overtopping in an abnormal state. To carry out the physical experiment in a wave flume, the model structure was reduced to a scale of 1/36 compared to the field structure. The discharge of the wave overtopping, the uplift pressure acting on the under surface of a non-standing barrier, and the wave pressure acting in front of a standing barrier were measured to analyze the hydraulic characteristics of the movable barrier. The results show that the impulsive pressure acts on the movable barrier, although the overtopping discharge is less than the allowable limit. When designing a movable barrier at a full scale, engineers should consider the impulsive pressure to secure the barrier’s stability on the target site. Keywords: movable barrier; wave overtopping; wave pressure; storm surge; hydraulic experiment 1. Introduction The ports connecting marine and land transportation are expanding to perform various functions, such as waterfront space and eco-friendly facilities, as well as fundamental functions for commerce and the fishery. These ports also include functions to create safer coasts and ports through the reinforcement of existing facilities, in addition to the development of port peripheral areas linked with leisure facilities. Thus, it is necessary to comprehensively review the planning aspects of the development and use of port peripheral areas in harbor structures. Accordingly, the mutual influence of facilities in the hinterland is complicated by the topographical characteristics and economic and social functions of ports. However, in accordance with the trend of placing more emphasis on the quality of life, sensitivity to disasters caused by climate change has increased. Hence, the needs for harbor structures to reduce disasters has increased. In particular, in areas where serious disasters are expected, the interest for disaster-reducing facilities is high. As global warming due to climate change is expected to increase the intensity and frequency of typhoons [1], storm surges must be urgently prevented because of an increase in the expected casualties and flood damage. As typhoon intensity is expected to increase because of the rising sea levels and temperatures due to the effects of global warming [2], the damage caused by storm surges is expected to increase rapidly. Hence, the requirement to reinforce coastal structures has increased with increases in wave height. Coastal and water side areas should be especially protected from inundation by wave overtopping. To quantify wave overtopping in coastal areas, the EurOtop manual provides empirical formulas for various coastal structures through physical experiments [3], and a numerical model was developed to apply simple harbor geometry [4]. Various types of barriers have been constructed to prevent such inundation. The Eider Barrier of the radial gate type was built in 1973, in Germany [5]. This barrier is part of the dike defense line of the North Friesian coast. In England, the Thames Barrier Appl. Sci. 2020, 10, 89; doi:10.3390/app10010089 www.mdpi.com/journal/applsci Appl. Sci. 2019, 9, x FOR PEER REVIEW 2 of 15 coast. In England, the Thames Barrier was built in 1982 to prevent inundation by high tides (with floods from the upstream of the Thames) and had its official opening in 1984 [6]. Gates of the rotary segment type are normally located on a flat face flush with the river bed when in the gate housing and then rotated 90 degree to close the barrier in an emergency. In 1953, the south-western area of the Netherlands was threatened by a severe storm and was flooded by sea water. After this disaster, the storm surge barrier called the Maeslant Barrier was built in 1997, in the Netherlands [7]. This barrier consists of two sector-gates. The same type of barrier, called the St. Petersburg Flood Appl. Sci.Protection2020, 10, Barrier, 89 was built in 2011 in Russia [8]. In a normal state, these gates are parked in docks.2 of 14 However, these gates are moved to the center of the waterway to close the channel during severe storms. In 2013, the Venice Flood Barrier, which is one the first four gates of the MOSE project, was was builtbuilt inat the 1982 Lido to preventinlet in Italy inundation [9]. These by gates high of tidesthe flap (with type floods are raised from by the compressed upstream air of pumped the Thames) and hadinto itseach offi hollowcial opening gate. in 1984 [6]. Gates of the rotary segment type are normally located on a flat face flushRecently, with the a river movable bed whenbarrier in type the was gate proposed, housing andsuch then as a rotatedflap type 90 that degree could to be close installed the barrier on in an emergency.the revetment, In1953, as shown the south-westernin Figure 1 [10]. areaThis barrie of ther Netherlandsis usually used was as a threatenedtourist deck bybuta stands severe up storm to prevent wave overtopping when a storm surge occurs. Movable barriers should have an effective and was flooded by sea water. After this disaster, the storm surge barrier called the Maeslant Barrier operational method and the ability to adequately block against wave overtopping. A movable was builtbarrier in is 1997, composed in the of Netherlands a double deck, [7]. Thiswith barriertwo hinges consists installed of two on the sector-gates. upper deck. The Hinges same are type of barrier,installed called at the the St. end Petersburg of the deckFlood and the Protection middle of Barrier,the deck. was When built the inupper 2011 deck in Russia on the [land8]. In side a normal is state,pushed these gates by the are actuators, parked inthe docks. barrier However, stands in thesethe form gates of area triangle moved since to the rotation center occurs of the at waterway the to closehinge. the To channel resist duringupward severe forces, storms. such as Inthe 2013, uplift the force, Venice three-axis Flood Barrier, bearings which are installed is one the on firstthe four gateslower of the deck. MOSE The project, height was of the built movable at the Lidobarrier inlet can in be Italy adjusted [9]. These to prevent gates ofinundation the flap type by wave are raised by compressedovertopping air via pumped the designed into each conditions hollow gate.at the target site. However, impulsive pressure can Recently,occasionally a movableoccur at a barrier barrier typesuch as was a vertical proposed, wall, such even as though a flap the type barrier that properly could be blocks installed wave on the revetment,overtopping. as shown Thus, in it Figure is important1[ 10]. to This carry barrier out ph isysical usually experiments used as ato tourist accurately deck determine but stands the up to designed wave force [11]. prevent wave overtopping when a storm surge occurs. Movable barriers should have an effective In this study, a movable barrier is considered on the revetment of Haeundae Marine City in operationalBusan, Republic method andof Korea. the ability The design to adequately of the movable block barrier against is carried wave overtopping. out for the target A movable site, unlike barrier is composedthe developed of a double movable deck, barrier with [10]. two However, hinges the installed operation on method the upper and deck. the purpose Hinges are are the installed same at the endas those of the of deck the anddeveloped the middle movable of thebarrier, deck. as When shown the in upper Figure deck 1. A onphysical the land experiment side is pushed was by the actuators,conducted the to quantitatively barrier stands analyze in the the form discharge of a triangle of wave since overtopping rotation occursin a wave at theflume, hinge. and Tothe resist upwardwave forces, pressures such acting as the on uplift the movable force, three-axis barrier are bearings later measured are installed to determine on the lower the occurrences deck. The of height of theimpulsive movable wave barrier pressure can be to adjusted reflect the to preventworking inundationdesign stage. by The wave model overtopping structure was via designed the designed conditionssimply at to the measure target site.data However,for a standing impulsive barrier pressure and a cannon-standing occasionally barrier. occur In at Section a barrier 2, suchthe as a verticalexperimental wall, even setup though and the test barrier condit properlyions of this blocks study wave are summarized. overtopping. In Thus,Section it 3, is the important results are to carry presented for the wave overtopping and wave pressure of the physical experiment. Finally, the out physical experiments to accurately determine the designed wave force [11]. conclusion is given in Section 4. (a) (b) FigureFigure 1. Sketch 1. Sketch of theof the developed developed movable movable barrier;barrier; ( (aa)) in in a anormal normal state; state; (b) ( inb) an in abnormal an abnormal state. state. In this study, a movable barrier is considered on the revetment of Haeundae Marine City in Busan, Republic of Korea. The design of the movable barrier is carried out for the target site, unlike the developed movable barrier [10].