Wave Height Reduction Research Articles

Wave height reduction through the under surface pipe structure model

The model of the subsurface pipe structure is designed as a reducer of the height of an incident wave generated. Part of the wave will be reflected, and some will be transmitted through the pipe structure. Experiments on the calculation of reflection and transmission coefficients on the subsurface pipe structure model were carried out with variations in the depth of water in the flume. This experimental study aims to determine the effect of changes in incident waves on variations in water depth above the subsurface pipe structure (d-h = 0.0h; 0.1h; 0.2h). This research was conducted at the Hydraulics Laboratory of the Department of Civil Engineering, Faculty of Engineering, Hasanuddin University. Experimental laboratory research method using a wave generator flume with the characteristics of the generated waves consisting of 3 variations of the period (T=1.0 seconds, T=1.1 seconds, T=1.2 seconds) with three variations of water depth (d) which used, i.e., d=1.0h; d=1,1h and d=1,2h, where h is the height of the pipe structure. The results of this study indicate that the deeper water above the structure, the smaller the reflection coefficient and the greater the transmission coefficient.

Evaluating Vegetation Effects on Wave Attenuation and Dune Erosion during Hurricane

This study employs the XBeach surfbeat model (XBSB) to explore the effects of vegetation on wave attenuation and dune erosion in a case study of Mexico Beach during Hurricane Michael. The XBSB model was validated against laboratory experiments of wave-induced dune erosion and wave attenuation by vegetation. In the case study of vegetation on dunes in Mexico Beach during Hurricane Michael, different vegetation drag coefficients were evaluated to investigate the effects of vegetation on wave attenuation and dune erosion. LiDAR data of dune profiles before and after Hurricane Michael were used for model validation. The findings reveal that vegetation on dunes significantly affects wave attenuation and dune erosion. Under vegetated conditions, as the vegetation drag coefficient value increases, wave attenuation also increases, leading to a reduction of dune erosion. An increase in vegetation density enhances wave attenuation in the vegetated area, including reductions in significant wave height and flow velocity. However, the rate of change in attenuation decreases as the vegetation density increases. Through simulations under regular wave condition on Mexico Beach, an optimal vegetation density was identified as 800 units/m2. Beyond this density, additional vegetation does not substantially improve wave attenuation. Furthermore, the position of the dune crest elevation is related to the location where the alongshore flow velocity begins to decrease. The findings highlight the essential role of coastal vegetation in enhancing coastal resilience against hurricanes.

Future Wave Climate-Driven Longshore Sediment Transport and Shoreline Evolution along the Southwestern Black Sea

This study investigates the future wave climate-driven longshore sediment transport (LST) and shoreline change on the Karasu Coast, situated on the southwestern coast of the Black Sea, under the RCP4.5 and RCP8.5 wave climate scenarios. Within the scope of this study, hourly deep sea wave data between 2021 and 2100, according to the RCP4.5 and RCP8.5, were used in order to predict future LST processes. Net and gross LST rates were computed using various empirical and numerical methods based on hourly wave parameters. By the conclusion of the study period after 80 years, the average net LST rates were obtained as 48,000 and 51,500 m3/year in the RCP4.5 and RCP8.5, respectively, while the gross LST rates were 250,000 and 255,000 m3/year. Due to the increase in wave height and period in both climate scenarios compared to the historical data, the average gross LST rates are projected to rise in the future. The reduction in swell wave heights, coupled with an increase in wind wave heights, compared to the past has led to a reduction in net LST. The results show that, after 80 years, LST will have increased 2.5 times more in the near future in comparison with the middle future for both scenarios.

Analysis of the Bending Height of Flexible Marine Vegetation

Marine vegetation is increasingly viewed as a living shoreline that protects coastal communities and ecosystems from the damaging effects of wave energy. Many studies have explored the potential of marine vegetation in terms of reducing wave height, but more work is needed. Here, we used particle image velocimetry, fluid–structure interaction simulation, and multiple regression analysis to estimate the bending behaviors of flexible marine vegetation in water flow, and we predicted the wave height reduction in the downstream vegetation meadow. We considered different vegetation types and water flow velocities, constructed a total of 64 cases, and derived a multiple regression equation that simply estimates the vegetation bending height with a tolerance of ~10%. When the bending height rather than the vegetation height was applied, wave height reduction was alleviated by 1.08–9.23%. Thus, flexible vegetation reduced wave height by up to ~10% less than rigid vegetation in our investigation range. This implies that the impact of bending behavior becomes more pronounced with a larger vegetation meadow. The relative % decrease in wave height reduction was greater for fully submerged vegetation compared to partially submerged vegetation.

Physical Experiments Of Wave Attenuation Over Submerged Shellfish Reefs

Globally and across Australia shellfish reef ecosystems have become critically endangered due to decades of overfishing, pollution and dredging (e.g., Beck et al., 2011). In response, the Australian federal government, in partnership with The Nature Conservancy, committed to restoring 60 shellfish reef ecosystems across Australia by building reefs from limestone and recycled shells scattered with juvenile oysters or mussels. Although the primary aim is to promote healthy marine ecosystems and biodiversity, there are strong indications that these restored shellfish reefs may also substantially dissipate ocean waves and provide protection against coastal flooding. Analogies have been drawn with conventional engineering structures (submerged breakwaters, e.g. Dattatri et al., 1978) as well as nearshore shellfish reefs increasingly considered as a nature-based method for coastal resilience against flooding (“living shorelines”, see e.g. Morris et al., 2021). Although the currently restored reefs do present clear similarities, they also have distinct differences that raise questions to whether they can be as effective in dissipating wave energy. Observational data from laboratory or field to verify this is currently lacking. This study aims to quantify the effectiveness of multiple parallel submerged reef structures in relatively deep water in dissipating wave energy. Experiments (1:10 scale) were carried out in a 54-m-long wave flume using 3 reef designs that vary in reef spacing, width and height, representative for shellfish reef ecosystems as recently restored and established across Australia and the US. All designs were subjected to two water depths (0.7 and 1 m on laboratory scale) and 8 (irregular) wave conditions covering 4 peak wave periods and significant wave heights ranging from 0.1 to 0.3 m (lab scale). For the cases with 0.7 m water depth, wave height reduction varied from 10 to 23%, while for the cases with 1 m water depth wave heights generally decreased slightly up to about 5%. The reefs were found to be particularly effective in reducing the largest waves within the timeseries that would have the highest potential of causing coastal impact (e.g., flooding or erosion). In addition, observations obtained with an Acoustic Doppler Velocimeter showed up to 45% reduction of near-bed orbital (rms) velocities, highlighting the potential for these structures to benefit seagrass restoration efforts. Overall, the results of this study show that restored shellfish reefs can reduce incident wave energy and orbital velocities considerably, in particular for relatively high waves in relatively shallow water, and have the potential to be considered in nature-based coastal defense strategies.

PHYSICAL MODELLING OF NATURAL COASTAL PROTECTION SYSTEM: CONTRIBUTION OF GREEN MUSSELS TO THE EFFECTIVENESS OF NATURAL COASTAL PROTECTION SYSTEMS

Indonesia is an archipelago with a long coastline which provides many economic, social, and cultural advantages. Therefore, it is necessary to protect coastal areas from erosion. Mangroves as a form of natural coastal protection, are economically and environmentally feasible in many coastal areas. However, before mangroves can grow into strong trees which require two years of plantation, the ocean waves will damage them. To solve this problem, a natural coastal protection system using main natural protection (mangroves) as well as a temporary artificial structure (bamboo poles with green mussels) is proposed. This study aims to quantify wave height reduction using various mangroves and bamboo pole configurations. The laboratory experiments were conducted in a wave flume using physical models of mangroves as the main natural protection and bamboo poles with green mussels as the temporary artificial structure. Various wave conditions, including extreme waves, were generated during the laboratory test. This paper focuses on wave transmission over the natural coastal protection system to determine the most effective configuration of bamboo poles with green mussels. The results show that the most effective configuration model is to use 50 mm between the poles’ columns and rows and a breakwater width of 800 mm.

Meteotsunamis in the Tamsui River estuary, Taiwan

This study presents meteotsunami evolution and statistics in the Tamsui River estuarine system from 12 years observations. In the tide-dominated estuary, a strong correlation is observed between high tidal levels and the upstream propagation of meteotsunami waves. Such long waves travel the Tamsui River at an average speed of 6 m/s, while their speed slightly decreases to 4 m/s in the upstream rivers. The propagation changes are likely due to the contraction channel and shallow depth of the upstream rivers. During the upstream propagation, low-frequency waves (an average period of 44.5 min) have the significantly low reduction of wave height compared to high-frequency waves (an average period of 21.5 min). Findings suggest that low-frequency waves are capable of propagating over longer distances within the river estuary than high-frequency waves. In terms of long-term statistical analysis in 2014–2020, meteotsunamis predominantly occur in late winter and early spring. These events are primarily triggered by cluster and frontal convective storms, which are predominant atmospheric forcings responsible for initiating meteotsunami waves. These convective storms are often associated with incoming cold surges or cold fronts crossing the Taiwan Strait, which has implications on the role of pressure and wind disturbances, as well as the resonance mechanism in meteotsunami initiation. Furthermore, the study assesses the probability of meteotsunami occurrences, revealing that an annual prediction of wave height can reach up to 0.3 m. This finding raises concerns regarding potential hazards in Taipei City, where the population exceeds 6.8 million people. Of particular concern is the vulnerability of the Keelung River, which flows through the city center. In summary, the potential hazards posed by meteotsunamis in the Tamsui River estuary underscore the importance of risk management and preparedness measures.

Multi-objective decision tool for the assessment of co-located wave-wind offshore floating energy parks

This study explores the benefits of co-locating wave-wind offshore energy parks. It focuses on the leeward effects of hypothetical wave energy converter (WEC) arrays deployed offshore Viana do Castelo, Portugal, and their synergies with the WindFloat Atlantic wind farm. Wave propagation through arrays of CECO WECs and their near-field effects were simulated using SNL-SWAN model. Furthermore, a multi-objective function to evaluate and choose between WEC arrays was defined. The analysis considered a wave height reduction area index, the q-factor and a new wave energy park layout assessment index (WLA). The effectiveness of arrays was dependent on incident wave direction, layouts with larger spacing achieved higher q-factors, while lower spacing provided better shield protection. The WLA, which considers both power absorption and wave height reduction, was introduced as a decision-making tool. The results also showed that some arrangements could increase accessibility to the turbines by circa 22%, representing about 1957 h/year added to the weather window for maintenance and operation of the park. In summary, this study provides a comprehensive analysis and a decision-making strategy for determining the optimal positioning of WEC arrays, contributing to the advancement of renewable energy technologies, promoting sustainable and efficient utilization of wave and wind resources.

Selection of cross sections for solitary wave transmission efficient for submeged vertical porous breakwater using Flow-3D model

Climate change is causing progressively severe coastal erosion, especially in beaches and tourist areas. Vertical porous breakwaters were chosen to protect the beaches for their effectiveness in reducing waves and preventing erosion. However, submerged vertical porous breakwaters must be applied due to the characteristics of beaches that do not allow shielding. Thus, the width of the porous breakwaters should be increased, incurring construction costs. This study proposes cross-sections of submerged vertical porous breakwaters that have the same width and determines the selected cross-section in those sections that effectively meets the wave height reduction. The Flow-3D numerical model with porous structures and solitary wave boundary conditions was used to simulate 72 scenarios of the interactions between solitary waves and submerged vertical porous breakwaters. The selected cross-section is a parallel configuration, where the distance between the two breakwaters is twice the width of the first breakwater. Dimensionless graph systems defining parallel breakwater parameters according to incoming solitary waves were established.

Dynamic Performance of Suspended Pipelines with Permeable Wrappers under Solitary Waves

Submarine pipelines are widely adopted around the world for transporting oil and gas from offshore fields. They tend to be severely ruined by the extreme waves induced by the natural disaster, such as hurricanes and tsunamis. To maintain the safety and function integrity of the pipelines, porous media have been used to wrap them from the external loads by the submarine environment. The functions of the porous wrappers under the hydrodynamic impact remain to be uncovered before they are widely accepted by the industry. In this study, a numerical wave tank is established with the immersed boundary method as one of the computational fluid dynamics. The submarine pipelines and their porous wrappers are two-way-coupled in terms of displacement and pressure at their interfaces. The impact from the solitary waves, which approximately represent the extreme waves in the reality, on the pipelines with different configurations of the porous wrapper is investigated. The results present significant protective functions of the wrappers on the internal pipelines, transferring the impact forces from the pipelines to the wrappers. The protective effects tend to be enhanced by the porosity and thickness of the wrappers. The influence of the pipeline configurations and the marine environment are then analysed. As for the front pipeline, an increase in the gap leads to a slight increase in the horizontal forces on both the wrapper and the pipeline, but a significant increase in the vertical forces. As for the rear pipeline, because of the shield function of the front pipeline, the velocity within the gap space and the forces on the pipes are decreased with the decrease in the gap size. The complex flow fields around the pipelines with wrappers are also illuminated, implying that the protection function of the wrapper is enhanced by the wave height reduction.

BIOMIMICRY OF NATURAL REEF HYDRODYNAMICS IN AN ARTIFICIAL SPUR AND GROOVE REEF FORMATION

An artificial spur-and-groove (SAG) reef formation designed to perform as a submerged breakwater was studied. Not only do natural SAG reefs effectively attenuate waves, but they also create important circulation within the system that encourages the success of corals and the overall ecosystem. Modular components were developed and imported into the CFD software FLOW-3D® HYDRO to test the wave-structure interaction while adjusting the geometry of the structure, wave conditions, and depth due to tidal changes in environmental conditions similar to Moloka’i, Hawaii. Results showed highest wave height reduction with larger wave heights as well as lower submergence during low tide conditions.

Comparison of Performance of Straight- and V-shaped Vanes Applied as Energy Saving Device to High-speed Boats

Hull Vane® is a device, generally utilizing a straight vane, installed horizontally near the stern of a vessel below the water surface and oriented in the transverse direction of the vessel with the purpose to save fuel consumption and to increase the vessel’s comfort. Because the bottom-hull form of a ship is generally curved, a non-straight vane may be more effective than a straight one when applied as Hull Vane®. The purpose of this study is to investigate the effectiveness of a V-shaped vane when applied as Hull Vane® on a 31 m high-speed crew boat. The study utilizes a computational fluid dynamics (CFD) method. CFD results show that the Hull Vane® decreased the bow-up trim of the boat, affected the boat’s wetted surface area, and decreased the height of the waves generated by the boat. The wave-height reduction due to the V-shaped Hull Vane® is larger than the straight Hull Vane®. Further, the Hull Vane® significantly reduced the total resistance of the boat at Froude number Fr = 0.34 with a larger reduction resulted from the V-shaped Hull Vane® (25.09% reduction for the straight vane and 30.75% reduction for the V-shaped vane). The observed resistance reduction decreased with increasing speed, ascribed to a too-large vane’s lift. The V-shaped Hull Vane® is more effective than the straight Hull Vane® in reducing the total resistance of the boat.

Understanding ecosystem services for climate change resilience in coastal environments: a case study of low-canopy sub-tidal seagrass beds in Fiji

The Pacific Island Countries (PICs) are exposed to extreme wave conditions which are projected to be exacerbated by rising sea levels due to climate change, prompting the need for strategic planning of coastal communities and assets. Nature-based protection has been proposed as a sustainable solution to promote the resilience of coastal areas from physical impacts such as wave-induced erosion. In this study, we investigate the potential coastal protection service of shallow sub-tidal low-canopy seagrass beds, dominated by Halodule uninervis, on the rate of wave height and wave energy reduction on a barrier and fringing reefs. The data was collected using bottom-mounted pressure sensors to measure wave height and energy reduction as waves moved toward the shoreline across the seagrass beds. The results show that on average, the seagrass beds were able to reduce wave height by 30% and energy by 47% in both reef environments. These reduction rates are strongly influenced by water depth, seagrass characteristics and local reef conditions. Based on these results, seagrasses can strengthen the resilience of coastal shorelines to wave erosion, thus conserving healthy low-canopy seagrass habitats has measurable benefits for shoreline protection in Fiji and other PICs.

Using salt marshes for coastal protection: Effective but hard to get where needed most

Abstract Salt marshes fronting coastal structures, such as seawalls and dikes, may offer important ecosystem‐based coastal defence by reducing the wave loading and run‐up levels during storms. We question (i) how the long‐term salt marsh development in the Dutch Wadden Sea relates to the tidal‐flat foreshore bathymetry and (ii) how the wave run‐up onto dikes, which enhances the risk of dike failure, depends on foreshore bathymetry, the presence/absence of marshes, marsh vegetation properties, tidal range and wind exposure. We analysed 15 years of vegetation and bathymetry maps along the entire Dutch Wadden Sea coast, in combination with detailed process‐based measurements at five locations during 3 years, to understand where salt marshes naturally form and what features determine their contribution to coastal protection. The horizontal extent of marshes along the dikes remained relatively stable over the past decade. The presence of marshes was associated with higher elevations of adjacent tidal flats (above ~0.5 m NAP), while landward‐directed marsh retreat was associated with surface erosion of the fronting tidal flats. Wave run‐up during storms was lower at sites with wider marshes and higher foreshore elevations. This was attributed to the marsh attenuation effect, which led to a reduction in wave heights at the dike toe. As the tidal range varies across the Dutch Wadden Sea, areas to the East with generally higher water levels experienced higher wave run‐up. Synthesis and applications. We found that (i) marshes, where present, effectively protected the dikes from wave loading and (ii) the sites where marshes typically do not develop spontaneously were the most vulnerable to high wave run‐up. This catch‐22 problem implies that increasing reliance on nature‐based coastal defences along soft‐bottom coasts may require human interventions to stimulate marsh formation at the locations where it is most needed. Alternatively, ‘hard engineering’ solutions may remain necessary where implementing nature‐based solutions are either too costly, unachievable, or at the expense of other ecological values, such as causing the loss of mudflats that are important for migratory birds.

Wave transmission at low-crested structures

This paper investigates the wave transmission through artificial reefs utilised as low-crested breakwaters to mitigate coastal erosion and reduce wave energy. The study utilises the DualSPHysics smoothed particle hydrodynamics (SPH) solver to evaluate the effectiveness of such structures. Wave transmission coefficients were computed for various reef configurations and wave conditions. Results indicate that the shifted reef configuration provides a higher level of wave height reduction for non-breaking waves, while there is no significant difference for breaking waves. The study further reveals that the efficiency of the breakwater decreases with an increase in wave steepness. However, the total wave energy significantly decreases, leading to a gradual reduction in wave height as it travels further from the breakwater. The outcomes of this research can aid in the optimisation and design of artificial reefs for coastal protection.

Experimental and numerical assessment of marine flood reduction by coral reefs

Coral reefs are crucial components of oceanic ecosystems. Reefs play a vital role in providing habitats for marine life and serve as a natural wave barrier against high-energy marine floods generated by long-period waves such as tsunamis and storms. Here, we performed experimental studies and numerical analyses and compared the results to investigate coral reef-induced marine flood reduction. In this study, 3D-printed corals were used as they closely resembled actual coral reefs, and marine floods were generated using a rotatory crank system. The results showed that healthy corals decreased flow velocity and depth at the end of the coral zone by 22.2% and 13.5%, respectively. Different boundary wave characteristics and coral roughness were assessed using idealized bathymetry with a 1% gradient. Additionally, numerical simulations revealed that wave height reduction was as high as 51% for corals with a Manning roughness of 0.25. Both the experimental and numerical assessments indicate significant wave energy reduction, which was compared with non-dimensional parameters such as the Froude Number that showed similarity between the results and the ratio between water depth and coral extent, which differed owing to limitations.

Analysis of the effect of seed growth (Rhizophora apiculata) on the distance of land from the beach in of Pulau Sembilan Pangkalan Susu District Langkat Regency

Mangrove is a renewable resource that provides services related to the environment, such as abrasion protection, seawater control of incursion, reduction of sea wave height and speed, cleaning of water contaminants, among others, important to support living beings. Its objectives include to study and evaluate the impact of planting distance from the beach which is useful for increasing growth for mangrove ecosystem type Rhizophora apiculata and this study based on a complete randomized design (RAL) with treatment distance (J) consisting of 5 treatments (a) P0 (planting distance from the beach 41 meters), (b) P1 (planting distance from the beach 42 meters), (c) P2 (planting distance from the beach 43 meters), (d) P3 (distance from the beach 44 meters) (e) P4 (planting distance from the beach 45 meters). The percentage of plant growth is 100%. Observational Data on the measurement of height, diameter, leaf count, leaf size, and leaf area, that the treatment at planting distance can increase the growth of seedlings R. apiculata. Based on the results of the study the effect of planting distance on R. apiculata obtained in the treatment of P2 (planting distance from the beach 43 m) a seedling height value that was highest growth with a value of 198.0 cm or average 33.0 cm. The highest value of plant diameter obtained from the treatment of P3 (spacing 44 m) with a value of 7.74 mm or average 1.29 mm . The highest added value was found in treatment P1 with a value total number of 39.2 strands or average 6.5 strands. The increase in leaf area is 50.9 cm or average 8.4 cm which is found in the P2 treatment.

Wave Height Reduction Inside Pohang New Port, Korea, Due to the Construction of a Detached Breakwater

The effect of a detached breakwater, which was constructed to improve harbor tranquility inside Pohang New Port, was examined through the comparison of wave data measured before and after the construction of the breakwater. The observation data showed that the wave energy was effectively reduced by the breakwater, although the wave height measured outside the breakwater was higher after its construction. The wave energy was reduced in all of the measured wave-propagating directions, but it was also observed that the breakwater became less effective in protecting against northeastwaves than in protecting against NNE waves. The BOUSS-2D Boussinesq-type wave model was employed to analyze the pattern of wave propagation, showing that, before the breakwater’s construction, NE waves could directly enter the port, increasing the wave energy inside the port. After the breakwater’s construction, simulations showed that the detached breakwater effectively blocked the waves approaching the port from both the NNE and NE directions, although the wave heights of the waves from the extreme NE direction inside the port increased. Considering that the estimated probability of failing to preserve the port tranquility was only 0.2–0.5% for these extreme NE waves, it was concluded that no secondary structures were necessary, and the existing breakwater was sufficient for the protection of the port.

Flood Modeling in Coastal Cities and Flow through Vegetated BMPs: Conceptual Design

Undeniably, climate-change-induced sea-level rise has served as a powerful driving force for the occurrence of coastal storms more severe than ever before. Low-lying metropolitan coastal areas, in particular, have become increasingly vulnerable to coastal flooding as a result of the rapid expansion of urbanization along flood-prone areas. Safeguarding coastal communities from the repercussions of flooding through the utilization of best management practices (BMPs) is one of the most effective ways of alleviating the situation. However, solely relying on inshore BMPs might not be the best possible approach when the storm event’s intensity can be reduced before the storm reaches the shoreline through the installment of offshore BMPs. Moreover, many recent studies have confirmed the cost-effectiveness and usefulness of natural elements, especially when combined with engineering solutions. This paper assesses the overall suitability and effectiveness of various combinations of nature-based inshore and offshore BMPs for coastal flood mitigation of storms with different intensities with applications to the Southern Brooklyn area in New York City. Moreover, inevitable conditions stemming from climate variability and change have made the assumption of stationary recurrence of extreme events unreliable. Furthermore, historical events of remarkable impacts have not been considered differently in the attainment of the flood design values. Thus, as one of the main objectives of this study, and in order to consider both, a nonstationary partial frequency analysis is utilized, including the major historical storms jointly with the precipitation data in the study area to obtain 100-year flood design values. To achieve the goals of the study, first, the offshore simulation was carried out using the Delft3D hydrodynamic model, developed by Deltares, in order to find the water level hydrograph for the ungauged areas of interest, with and without offshore BMPs followed by the simulation of the flood events on the inland coastal area using gridded surface subsurface hydrologic analysis (GSSHA), a module of the watershed modeling system (WMS) developed by the USACE, to assess the effectiveness of inshore BMPs. The proposed scenarios are tested against Superstorm Sandy, Hurricane Irene, and the 100-year flood hydrographs. The results showed a remarkable coastal flood wave height and water level reduction when integrating offshore and inshore green BMPs.

Coastal Protection by Planted Mangrove Forest during Typhoon Mangkhut

Mangroves provide many ecosystem services, including coastal protection against storm surges and waves. As an adaptive method for coastal defense, mangroves were widely restored and planted in tropical and subtropical regions, such as the coastal regions in Southeast Asia. Field surveys were conducted to quantify the nature-based coastal protection provided by a planted mangrove forest along the coasts of Shanwei, Guangdong Province, China, under typhoon influence. The resilience of mangrove trees was assessed under the impact of Typhoon Mangkhut (2018), which induced a maximum storm surge of 1.74 m with a maximum wave height of 1.16 m in the study area. The pre- and post-typhoon surveys and hydrodynamic measurements were conducted at a mudflat with planted mangroves. The wave height reduction reached 77% over 100 m wide mangrove forest. Our results suggest that a six-year-old planted mangrove forest with a ~100 m width might withstand a super typhoon impact and provide substantial protection for the fish ponds and embankments behind the mangrove forest. No uproots or deadly breakage of stems were observed in the mangrove forest, while severe defoliation was spotted for a small portion of trees in the study area, mainly along the wind path, the windward edge of the forest, and among the taller plants. Obvious sedimentation in the mangrove front and the tidal flat was observed during the typhoon Mangkhut (2018) and the entire typhoon season of 2018.