Coastal Research Research Articles

Measured Fate of Beach Nourishment Sand

Houston, J.R., 2023. Measured fate of beach nourishment sand. Journal of Coastal Research, 39(3), 407–417. Charlotte (North Carolina), ISSN 0749-0208. The fate of sand placed over a 20-year period in one of the largest series of beach nourishment projects ever conducted in the United States is determined by using direct measurements of elevation vs. distance from dunes to closure depth. Four projects placed 11.25 million m3 of sand from 1998–2017 on a 28.8-km-long shoreline at Panama City on Florida's Gulf of Mexico coast. Profile measurements were available in 1996 following Hurricane Opal and in 2018 after Hurricane Michael, one of the largest hurricanes to strike the United States, which came ashore only 30 km from Panama City beaches. The profiles were about 300 m apart within the project template and extended down to closure depth. After about 20 years, 87 ± 3% of the nourishment sand remained on profiles. Some sand used for nourishment was dredged within closure depth along a 3.6-km section and resulted in sand loss of 4% ± 1% as sand partially refilled the dredged holes. About 9% ± 3% was lost to longshore transport out of the project area. Calculations based on the equilibrium profile concept used in U.S. beach nourishment design predicted beaches should have widened 30.9 m ± 0.9 m and profiles raised 0.69 m ± 0.10 m due to the measured volume of sand remaining on profiles from the start of beach nourishment in 1998 to November 2018 after Hurricane Michael. The measured change in beach width was 32.4 m ± 4.0 m, and the rise was 0.66 m ± 0.05 m. The rise of 0.66–0.69 m is comparable to the 0.81 m mean sea-level rise by the year 2100 projected by the Intergovernmental Panel on Climate Change for its worst-case temperature scenario.

Influence of Hook Number on Species Composition, Catch Rate, and Size of Needlefishes in the Gulf of Mannar, India

Naganandhini, V.; Muthupandi, K.; Vasanth, K.; Neethiselvan, N.; Padmavathy, P., and Radhakrishnan, K., 2023. Influence of hook number on species composition, catch rate, and size of needlefishes in the Gulf of Mannar, India. Journal of Coastal Research, 39(3), 502–508. Charlotte (North Carolina), ISSN 0749-0208. The contribution of needlefishes from the Gulf of Mannar coast has been remarkable and is presently exploited by pelagic longlines. The J hook is extensively used in longline fishing in the Indian region to capture carnivore fishes, including needlefish. Catch rate significantly differed between the hook numbers. In this context, three hook numbers of 10 J, 11 J, and 12 J were studied from January to May 2022. Results showed that the Ablennes hians was the dominant fish caught (47.9%), followed by Tylosurus crocodiles (22.2%), T. choram (16.6%), and Strongylura strongylura (13.3%); weight-based catches of T. crocodiles (39.7%) were dominantly higher, followed by A. hians (35.9%), T. choram (13.8%), and S. strongylura (10.6%). The two-way ANOVA results revealed that a significant (p <0.05) difference occurred between the hook number and the number of species caught. The largest number of fish were caught with hook number 12 (3769), followed by hook number 11 (2745) and hook number 10 (1445). However, the highest weight of 2749.74 kg was recorded with hook number 11 and the lowest of 1602.65 kg in hook number 10 (p <0.05). This is related to fewer fish caught with hook number 10 and heavy fishing pressure on subadults (<50 cm) due to the use of hook number 12. Considering the maximum total length and weight, the optimum hook number for the commercial exploitation of needlefishes was hook number 11. The catch per unit effort disproportionately increased with the increasing of the hook number; the significant higher contribution of 48.25 individuals/1000 hooks was from hook number 12, whereas hook numbers 11 and 10 were 35.13 individuals/1000 hooks and 18.51 individuals/1000 hooks, respectively.

Comparison of the Characteristics of Internal Wave Propagation under Two Surface-Boundary Conditions in Continuously Density-Stratified Oceans

Zhang, H.-s.; He, L.; Zhang, Z.-h., and Zhang, Y., 2023. Comparison of the characteristics of internal wave propagation under two surface boundary-conditions in continuously density-stratified oceans. Journal of Coastal Research, 39(2), 303–316. Charlotte (North Carolina), ISSN 0749-0208. Complete theoretical solutions were developed for the propagation of internal waves (IWs) with small amplitudes in a continuously density-stratified ocean under the free surface-boundary condition and rigid lid assumption. Additionally, a numerical model was established for the propagation of IWs under the free surface-boundary condition. In the proposed model, the Euler equations are employed as the governing equations and are discretized with an improved SIMPLE algorithm. In waters with a constant depth, a comparison between the numerical and theoretical results proved the reasonability and accuracy of the proposed method. Additionally, the numerical results under the free surface-boundary condition were compared with those under the rigid lid assumption to analyse the differences between the calculated velocities and density fields. Herein, the influences of characteristic parameters, including the period and amplitude of the incident waves and the coefficient of density and the mode number on the velocity fields under the two surface-boundary conditions, are discussed thoroughly. In the waters with nonuniform varied depths, numerical simulations on the IWs propagation were performed under the two surface-boundary conditions. Differences between the calculated physical fields of IWs in front of and behind the submerged dike are discussed. The detailed analyses showed that differences exist between the calculation results under the two surface-boundary conditions. In particular, they were obvious for the cases with high mode number and variable topography. The results are significant considering the propagation mechanism of IWs under different surface-boundary conditions in a continuously density-stratified ocean.

Wastewater Treatment of Solid Waste Leachate and Production of Proteinaceous Biomass Using Duckweed Vegetation ( Lemna minor )

Tekoğul, H., 2023. Wastewater treatment of solid waste leachate and production of proteinaceous biomass using duckweed vegetation (Lemna minor). Journal of Coastal Research, 39(2), 296–302. Charlotte (North Carolina), ISSN 0749-0208. Phytoremediation provides cost–effective wastewater treatment and recovery of wastewater as rich biomass by aquatic plants and produces bioenergy and various important by-products. This study was carried out to treat solid waste leachate with Lemna minor L. and convert wastewater nutrients into protein-rich biomass by this aquatic plant. To create the experimental setups, L. minor was produced in wastewater at six dilution ratios: 100% (T1), 75% (T2), 50% (T3), 25% (T4), Hoagland medium with Lemna (T5c), and 100% wastewater without Lemna (T6). At the end of the 45-day study,the pH 7.00 (T5c) and 8.81, the protein yield rate (crude protein) in the trial groups was found to be T1 = 40.10%, T2 = 67.53%, T3 = 75.24%, T4 = 42.72%, and T5c = 85.00%. In the study, the T3 group showed the best performance in terms of initial weight, final weight, total biomass, specific growth rate, relative growth rate, and protein ratio in wastewater groups. The highest and lowest removal rates in leachate ranged between 85.40% (T4) and 56.50% (T1) for the NH4 +-N value, 14.20% (T4) and 4.73% (T2) for NO2-N, 16.96% (T4) and 6.53% (T3) for NO3-N, and 23.10% (T3) and 16.08% (T1) for PO4–3-P. The total biomass of the trial groups showed an average 50.55% increase from the baseline level. Although 46% biomass was obtained in the Hoagland medium with vegetative growth, a very high biomass of 61% was obtained in the T3 group of solid waste leachate containing dilute wastewater. As a result, phytoremediation is recommended as a solid option for the management of wastewater resources. This efficiency has shown that aquatic plants can be used in the treatment of wastewater and the obtained high protein biomass can be used in various ways, such as animal feed and bioenergy.

Propagation Characteristics of Seismic Waves in Shallow Sea Sedimentary Layers

Zhao, S.; Gu, D.; Guo, C.; Wang, X., and Zhang, J., 2023. Propagation characteristics of seismic waves in shallow sea sedimentary layers. Journal of Coastal Research, 39(1), 32–44. Charlotte (North Carolina), ISSN 0749-0208. To explore new techniques for detecting and identifying targets in water, the propagation characteristics of seismic waves in shallow sea were deeply studied. Wave theory and staggered grid finite difference method were employed to analyze the propagation characteristics of seismic waves in a layer of underwater medium with a sedimentary layer. The results show that a Scholte wave is prone to disperse in an underwater medium with a sedimentary layer. The sediment thickness and acoustic parameters have great influence on the propagation characteristics of seismic waves. Moreover, the seismic wave signals were mainly concentrated below 20 Hz by collecting the vibration velocity of underwater interface. Furthermore, Scholte wave signals in underwater experiments were determined by utilizing four filtering methods and Scholte polarization characteristics, and the Butterworth filtering method can better preserve the integrity of vibration velocity signal. The theoretical, numerical, and experimental polarization characteristic results are basically consistent, which indicate that Scholte wave can be well extracted by the method of polarization characteristics.

Experimental Study of Tsunami Force Coefficients for Imwon Port on the East Coast of Korea

Baek, D.; Lee, B.W.; Ha, T.; Jang, S.-W., and Yoon, J.-S., 2023. Experimental study of tsunami force coefficients for Imwon Port on the east coast of Korea. Journal of Coastal Research, 39(1), 175–180. Charlotte (North Carolina), ISSN 0749-0208. A tsunami can cause severe damage to people and infrastructure in coastal areas through inundation caused by strong wave forces. In this study, three-dimensional hydraulic experiments were conducted to estimate tsunami force coefficients at Imwon Port, which is located on the eastern coast of the Korean peninsula. For hydraulic experiments, the offshore topography around the target area and the onshore structures in the port hinterland were modeled by applying the Froude similitude. Solitary waves were adopted as incident tsunami waves. The inundation water depths and tsunami forces were mainly measured in the onshore region to estimate the tsunami force coefficients. The tsunami force coefficients obtained at Imwon Port ranged from 0.85 to 5.27. The maximum wave forces and inundation depth were observed at the forefront structures closest to the shoreline among the measuring points. The tsunami force coefficients estimated for Imwon Port in this study can help to establish the design criteria for preventing tsunami disasters.

The Effect of Prosopis juliflora (Fabaceae) on the Physical and Chemical Properties of Coastal Dune Soil in Western Mexico

Vargas-Lomelín, J.G.; Macías-Rodríguez, M.Á.; Zarazúa-Villaseñor, P.; Rodríguez-Zaragoza, F.A.; Neri-Luna, C., and Albuquerque, F., 2023. The effect of Prosopis juliflora (Fabaceae) on the physical and chemical properties of coastal dune soil in western Mexico. Journal of Coastal Research, 39(1), 63–72. Charlotte (North Carolina), ISSN 0749-0208. Prosopis juliflora (Fabaceae) is a dominant legume and potential ecosystem engineer in the dunes of Jalisco, western Mexico. The objective of the present study was to evaluate how P. juliflora modifies soil physical and chemical properties in three coastal dunes that belong to different watersheds. To determine the physical properties of the three sites, soil samples were taken inside the canopy of five P. juliflora trees and five soil samples were taken outside their canopies. The same trees and soil positions regarding the canopy of P. juliflora were considered to determine the chemical properties, but the samples were taken at two different depths. A multidimensional and permutational analysis of variance (PERMANOVA) was performed to evaluate differences in the physical properties among the sites and between the sampling positions relative to the canopy of P. juliflora. This PERMANOVA also evaluated differences among sites, sample depths, and the positions of the samples relative to the P. juliflora canopy. A test of homogeneity of dispersions was performed to determine the data dispersion type, whereas a similarity percentage analysis identified which variables contributed most to the observed differences. A principal coordinate analysis was performed to visualize the differences in the model. The results demonstrated that P. juliflora modified the soil physical properties, specifically the real density, total porosity percentage, and percentages of silt and clay. The soil physical properties also varied significantly among the three sites. In addition, P. juliflora modified the soil chemical properties, increasing the electrical conductivity, pH, and total nitrogen, iron, and available phosphorus content. The results show significant differences between the two soil depths, as well as among sites. Ultimately, this study contributes to understanding of the implications of soil property modifications by plants in coastal dunes, which will give guidelines for managing and conserving these ecosystems.

Abiotic Stress Tolerance of Juvenile Small Abalone Haliotis diversicolor aquatilis (Obunjagi) to Gamma Irradiation

Jwa, M.S. and Hong, C.-Y., 2023. Abiotic stress tolerance of juvenile small abalone Haliotis diversicolor aquatilis (obunjagi) to gamma irradiation. Journal of Coastal Research, 39(1), 55–62. Charlotte (North Carolina), ISSN 0749-0208. In South Korea, the small abalone (obunjagi), Haliotis diversicolor aquatilis, is a prominent commercial seafood species. However, summer circumstances frequently impede abalone productivity, emphasizing the need for suitable approaches to promote abalone viability. The purpose of this study was to see if the survival rate and physiological responses of juvenile H. diversicolor aquatilis changed after exposure to low-level 60Co-gamma irradiation under high temperature (HT) and low salinity (LS) stress conditions (20 Gy). For this research, juvenile small obunjagi, H. diversicolor aquatilis, were obtained from Jeju City fishing vendors, Korea. Before the experiment, all abalone samples were acclimated for 7 days in a seawater-filled tank at 23°C ± 0.3°C and 32 ± 0.2 psu under starvation conditions. Seventy abalones (20 male and 50 female) were gamma irradiated and 30 abalones (10 male and 20 female) were used as controls. After 6 weeks of malnutrition, abalone survivability and the quantity of cardiovascular hemocytes rose dramatically after 20-Gy exposure compared with the control (0 Gy). The viability of abalone was dramatically reduced by HT stress but not by LS stress. The initially improved immune response-mediated hormetic impact might be connected to abalone survival rate under famine and HT stress, and the hormesis-induced gamma radiation exposure strategy will successfully raise abalone productivity throughout summer.

Energy-harvesting Efficiency Analysis of Ocean Currents: Proposing a Flow-induced Vibration Power-Generation System with Linear Generator Damping

Bai, X.; Sun, M.; Niu, J.J.; Sun, H., and Sun, L.P., 2023. Energy-harvesting efficiency analysis of ocean currents: Proposing a flow-induced vibration power-generation system with linear generator damping. Journal of Coastal Research, 39(1), 73–82. Charlotte (North Carolina), ISSN 0749-0208. The ocean current energy generation based on flow-induced vibration has mostly adopted a rotary generator, until now. In consideration of the possible shortcomings of the Vortex Induced Vibration for Aquatic Clean Energy system based on the rotary generator, this paper proposes a flow-induced coupling between the linear generator and the vibrator. For the vibration power-generation system model, this paper proposes a flow-induced vibration power-generation system model, in which the linear generator is directly coupled to the vibrator and the energy-harvesting efficiency is analyzed through numerical research methods. Results show that when the reduced velocity is 3.6 to 8.4, the energy conversion efficiency is greater and when the reduced velocity is 4.8 and the damping ratio is no more than 0.2, the maximum value of the energy conversion is 15.9%. The optimal efficiency can be achieved with the best combination of reduced velocity and damping ratio.

Storm Wave Characteristics during Typhoons Maysak and Haishen on the East and South Coasts of Korea

Seo, S.-C.; Kim, H.-J.; Hwang, T., and Lee, W.-D., 2023. Storm wave characteristics during Typhoons Maysak and Haishen on the east and south coasts of Korea. Journal of Coastal Research, 39(1), 129–142. Charlotte (North Carolina), ISSN 0749-0208. Typhoons Maysak and Haishen, the ninth and tenth typhoons of 2020, ravaged the Korean Peninsula within an interval of only 4 to 5 days. In the vicinity of the peninsula, these two typhoons exhibited unusual northward movement paths as they made landfall on the south coast of Korea and exited off the east coast. The storm waves caused by these typhoons damaged a number of structures along the east and south coasts, particularly by overtopping and flooding. In this study, storm waves were estimated by applying the wind fields caused by Typhoons Maysak and Haishen in the third-generation wave model Simulation WAves Nearshore (SWAN), and results were verified through a comparison with wave observation data. The storm wave characteristics were analyzed mainly based on the east and south coasts, which were damaged by high waves that accompanied the typhoons. In addition, the deep-water design wave specifications around the Korean Peninsula revised in 2019 were compared with the storm waves that occurred during Typhoons Maysak and Haishen as calculated by the SWAN model. Consequently, during the onslaughts of Typhoons Maysak and Haishen, storm waves corresponding to more than 90% of the deep-water design wave heights for the 50 year return period were estimated at grid points on the East Sea and Ulleungdo Island of Korea.

Shoreline Variation Prediction of the Jeongdongjin Sea Area Considering Effective Sediment Volumes

Kim, Y.-j. and Yoon, J.-s., 2023. Shoreline variation prediction of the Jeongdongjin Sea area considering effective sediment volumes. Journal of Coastal Research, 39(1), 154–166. Charlotte (North Carolina), ISSN 0749-0208. The coastal erosion in the East Sea region of Korea has been increasing because of the imbalance in the effective sediment volume and sediment transport from coasts and rivers, which causes intermittent erosion and sedimentation. The accurate prediction of the coastal sediment budget is an extremely difficult task because the sediment transport mechanism on the coast is highly complex. Studies considering the effective sediment volume supplied through rivers remain limited, although many other studies have focused on identifying the characteristics of sediment transport on the east coast. The grain-size distribution of the soil on the coast is considered the single-grain size (D50); however, the grain-size distribution of sediments flowing into and out of the coast and the topographical characteristics of the sea area need to be considered to predict shoreline variation with a high degree of accuracy. Thus, this study conducts in-depth analysis on the changing state of soil movement in wave-current co-existing fields (mountain, river, and coastal areas). The objective is to predict shoreline variation considering the environment of the Jeongdongjin Sea area by establishing a quantitative evaluation system of the effective sediment volume discharged from the area of river mouth bars. An effective sediment volume was evaluated using a sediment runoff model; the wave transformation for each survey line was calculated using SWAN to consider the wave characteristics acting on the sea area. The prediction performance was greatly improved by applying the mixed grain size to the soil in the sea area and by applying jetties to the reefs for upgrading the prediction of the shoreline variation.

Prediction of Wave Conditions Using a Machine Learning Framework on the East Coast of Korea

Kim, T. and Lee, W.-D., 2023. Prediction of wave conditions using a machine learning framework on the east coast of Korea. Journal of Coastal Research, 39(1), 143–153. Charlotte (North Carolina), ISSN 0749-0208. Currently, technology for rapid and accurate wave information prediction is required because of the increase in human and property damage caused by high waves as a result of climate change on the east coast of Korea. Over the past few years, the volume of data produced has become large as the world enters the era of the fourth industrial revolution, and research on machine learning models that can use these data is actively being conducted. In this study, three machine learning models (XGBoost, support vector regression, and linear regression) were used to make accurate estimates of waves on the east coast of Korea, and the model suitable for the data was selected. The input data that were used to train the models included air barometric pressure, wind, and wave data collected using a deep-sea buoy (Donghae), and the data were used to construct models for predicting offshore wave heights and wave periods. Of the three models, XGBoost exhibited a Nash-Sutcliffe efficiency (NSE) of 0.89 and a root-mean-square error (RMSE) of 19.7 cm for wave height and an NSE of 0.81 and an RMSE of 0.66 s for wave period. XGBoost was selected as suitable for predicting offshore wave heights and wave periods at Maengbang on the east coast of Korea, and excellent and reliable consistency was observed between the observed and the predicted values. Because machine learning models have short computation times and high accuracy, they can become an alternative to conventional physics-based wave models.

Beach Erosion along the Eastern Coast of Korea: A Brief Review

Lim, H.S.; Lee, H.J.; Kim, D., and Hong, S., 2023. Beach erosion along the eastern coast of Korea: A brief review. Journal of Coastal Research, 39(1), 181–190. Charlotte (North Carolina), ISSN 0749-0208. Most of the beaches on the eastern coast of Korea are eroding at an alarming rate, triggered by combined natural and artificial causes. In this review, each of the major causes of beach erosion is addressed briefly. A few protection measures such as breakwaters and nourishments are also discussed, with the emphasis on the unexpected or undesirable outcomes. Finally, some of the essential requirements for the field measurements in a beach are mentioned. Global warming has induced the chief natural causes of the beach erosion in Korea, including a gradual increase in wave energies and sea level. An estimation in this review suggests the rates of shoreline of 1 m/10 yrs on the eastern coast by sea-level rise alone. By comparison, artificial beach erosion is most likely to occur upon emplacing structures nearby. A variety of the artificially erosional cases by beach developments are described in the review. Storms and typhoons play a critical role in eroding beaches and changing local morphologies in a short period of time and thus should be observed hydrodynamically. However, the diminishing run-off of rivers and streams should be regarded as the primary reason for the nationwide artificial erosion of beaches. The scanty supply of stream sands to the beaches, together with the influence of global warming, would have the beaches eroded continuously without any coastal developments.

Rock Archetypes Introduction

Rock Archetypes Introduction

Lagoon, Wetland, Till, and Ice Archetypes Introduction

Lagoon, Wetland, Till, and Ice Archetypes Introduction

Preliminary Analysis of Reclamation Changes in Macao Using Multisource and Multitemporal Remote-Sensing Data

Liu, Z.; Zang, J., and Liu, J., 2023. Preliminary analysis of reclamation changes in Macao using multisource and multitemporal remote-sensing data. Journal of Coastal Research, 39(1), 90–102. Charlotte (North Carolina), ISSN 0749-0208. Macao is a typical reclamation city. A systematic analysis of reclamation changes can be used to relate reclamation to socioeconomic development. In this study, multisource and multitemporal satellite remote-sensing data were used to analyze the temporal and spatial characteristics, driving forces for reclamation, and nearshore water quality of Macao. The results showed that the Macao coastline is moving towards the sea. The total area of Macao increased from 29.19 km2 in 1999 to 35.83 km2 in 2019. The largest proportion of reclamation land-use type was public facilities land, whereas the smallest proportion was green land and square land. The land distribution gradually became more compact up to 2007 and dispersed thereafter. The factors of population, gross domestic product, number of visitors to Macao, and total export trade had different influences on reclamation in Macao during different time periods, where the population factor had the largest overall impact. The concentrations of chlorophyll and suspended sediment in Macao coastal waters were high nearshore and low offshore.

Morphodynamics of Rip Current Systems at Haeundae Beach, Korea

Lee, J. and Hong, S., 2023. Morphodynamics of rip current systems at Haeundae Beach, Korea. Journal of Coastal Research, 39(1), 199–206. Charlotte (North Carolina), ISSN 0749-0208. Rip current generation and beach morphodynamics were measured for about 60 days at Haeundae Beach, Busan, Korea, using various instruments comprising co-located velocity and pressure sensors, ADCPs, and kinematic GPS surveys. Rip currents are narrow currents initiated close to the shoreline that flow strongly in a seaward direction through the surf zone and beyond. It is generally accepted that rip currents arise mostly from the variation of wave height alongshore attritutable to wave refraction over inhomogeneous bathymetry. Field measurement was performed to clarify the generation mechanism of rip currents at Haeundae Beach, Korea. The creation and destruction of sandbars could be identified clearly using data from a photogrammetric survey taken from the roof of a high building during the summer season. In this study, a surf-zone depth survey was performed periodically using Network Real-Time Kinematic GPS, a device that can provide a detailed topographic survey of the surf-zone region. Using these data, we perform a correlation analysis between rip current generation and surf-zone morphological variation.

Meteorological Water Surface Disturbance in Tsunami Frequency Band near Ulleung Island on the East Sea of Korea

Lee, E.; Shin, S.; Park, J.-N., and Park, S.-C., 2023. Meteorological water surface disturbance in tsunami frequency band near Ulleung Island on the East Sea of Korea. Journal of Coastal Research, 39(1), 191–198. Charlotte (North Carolina), ISSN 0749-0208. The probability of exposure to coastal hazards has been increasing recently due to climate change. Meteotsunamis, one of the coastal hazards, are generated around the world by meteorological forcing, and their frequency band is 2 minutes to 3 hours, similar to earthquake-induced tsunamis. Although the west coast of South Korea has been unexpectedly affected, incurring casualties and property losses in 2007 and 2008, there are no documented cases in the East Sea of Korea. However, the surge gauge located on Ulleung Island (the easternmost part of Korea), operated by Korea Meteorological Administration to detect tsunamis, observed two meteotsunamis in January and April 2020. So, this study aimed to quantify the two meteotsunamis based on sea-level measurements and atmospheric observations. The results of the study show the maximum peak-to-trough wave height was 99.86 cm greater than the wave height of the 2011 Tohoku tsunami obtained by the Ulleung surge gauge. This reveals that the meteotsunami monitoring system should be improved based on the deep analysis of sea level and atmospheric observations on the East Sea of Korea to respond to climate change.

Experimental Study on Hydrodynamic Performance of Partially Perforated-Wall Caisson Breakwaters Designed for the Southeast Coast of Korea

Lee, B.W.; Baek, D.; Ha, T.; Lee, K.J., and Yoon, J.-S., 2023. Experimental study on hydrodynamic performance of partially perforated-wall caisson breakwaters designed for the southeast coast of Korea. Journal of Coastal Research, 39(1), 167–174. Charlotte (North Carolina), ISSN 0749-0208. If a perforated wall is installed on the front and rear surfaces of the caisson, then it is possible to reduce the wave reflection and the discharge of wave overtopping caused by energy dissipation. Consequently, the energy dissipation helps reduce the transmitted wave and improve the stability of the breakwater. This paper discusses the hydraulic performance (i.e. the wave reflection, wave transmission, discharge of wave overtopping, and stability of breakwater) of four perforated breakwaters as measured by physical experiments in a wave flume. The irregular wave was generated by the wave condition of the target site. Three breakwaters were designed: a perforated wall with a single chamber for a 50-year return period and two perforated walls with double chambers for a 100-year return period. Based on experimental results, the breakwater with a double chamber showed the best performance of 0.612, 0.102, and 0.076 m3/(m · s) for the reflection, transmission coefficient, and overtopping discharge, respectively. In particular, in the stability experiment of the armor units and perforated caissons, the breakwater with double chamber has not experienced any failure in any of the test cases.

Using GIS and Multicriteria Analysis to Map Flood Risk Areas of the Tongo Bassa River Basin (Douala, Cameroon)

Sone Essoh, W.; Onguene, R.; Ndongo, B.; Nshagali, G.; Colmet-Daage, A.; Guillaume, M.; Iroume, J.; Stieglitz, T.; Besck, F.; Efole Ewoukem, T.; Tomedi Eyango, M.; Etame, J., and Braun, J.J., 2023. Using GIS and multicriteria analysis to map flood risk areas of the Tongo Bassa River Basin (Douala, Cameroon). Journal of Coastal Research, 39(3), 531–543. Charlotte (North Carolina), ISSN 0749-0208. The present study aimed to map the areas at risk of flooding in the Tongo Bassa watershed (42 km2) located in the heart of the Cameroonian economic capital (Douala) in the tropical zone of Central Africa, more precisely in the Wouri Estuary, at the bottom of the Gulf of Guinea. Like most of the world's major cities, Douala is subject to floods. The methodological approach was to identify the flooding risk determinants in the area from an extensive literature review and field surveys and then analyze these factors and map areas at risk of flooding using the analytical hierarchy process approach coupled with the GIS environment. The results revealed that four parameters of the natural environment (elevation, drainage density, distance to the river, and land cover) were the factors that mainly influenced the phenomenon of flooding in the region. Three major classes of flood risk were highlighted: low risk, medium risk, and high risk. To validate the effectiveness of the flood risk map obtained, the flood points collected in the field were cross-checked for ground truth after a flood occurred in the watershed. This cross-check between the resulting map and the flood points using GIS tools showed a good representation of the flooded area. This result is quite interesting because the areas where the risk of flooding is high are consistent with those where flooding is most frequent. The presented results constitute a basic decision support tool for the management of flood zones by the public authorities and the decentralized territorial communities of the city of Douala.