Correia, J.R.M.B.; Oliveira, W.D.M.; Pereira, P.S.; Camargo, J.M.R., and Araújo, M.E, 2018. Substrate zonation as a function of reef morphology: A case study in Carneiros Beach, Pernambuco, Brazil. In: Almar, R.; Almeida, L.P.; Trung Viet, N.; and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 1–9. Coconut Creek (Florida), ISSN 0749-0208.

Beachrocks or Sandstones reefs are characteristic formations of the northeast coast of Brazil. In addition to their ecological function (e.g., shelter for other organisms), they have an important economic and scientific value. A single topographic survey and reef's substrate identification was performed along 22 profiles (with 40 m spacing), using kinematic DGPS, in the Carneiros Beach's beachrock, located at the mouth of Formoso River (Pernambuco, Brazil). The aim of this survey was to characterize the reef's topography and its benthic cover. The consolidated substrate is located in the intertidal zone, between +2.02 and −1.66 meters depth contours. According to the topography, three sub-environments were identified: backreef, reef crest and forereef. The backreef was found to be the narrowest, with a steep slope on the ocean side. The reef crest showed a low variation in substrate cover while the forereef showed a greater variation and the largest width. Over the measured profiles 11 categories of reef substrate cover were identified. A clear distribution patterns were observed in sea urchins, seaweeds, scleractinian corals and the soft corals Palythoa caribaeorum, as well as a sparse occurrences in the hydrocoral Millepora alcicornis and sponges. It was observed that the pattern of distribution of algae and hard corals were related to the local hydrodynamic conditions. The results of this study indicate that several factors can influence the spatial distribuition of the benthic cover. On the reef profiles studied, we observed a substrate zonation relating to the air exposure gradient, variation of tides, unconsolidated substrate deposition and wave action. In addition to these environmental factors, anthropogenic actions, such as trampling, may be responsible for changes in this environment. This study represents a baseline for future surveys of the spatial distribution of organisms.

Thoreux, T.; Sakho, I.; Sall, M.; Testut, L., and Woppelmann, G., 2018. Trends in sea level around the Cap Vert peninsula, Senegal. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 10–13. Coconut Creek (Florida), ISSN 0749-0208.

The variations of the coastline have a great impact on the human activities. Natural mechanisms such as the nearshore sediment transport, non-climatic background geological processes (e.g., land subsidence) or the sea level variations are three important factors that control coastline position. During more than one century, the third process has been extensively studied, at a global scale, using datasets obtained from tide gauges. Sea level observations on the West African coastline are scarse. As an example, the tide gauges in Dakar (Senegal) and in Takoradi (Ghana), are the only ones in West Africa with temporal series longer than 40 years. Such limited amount of data difficults the devevelopment of sea level studies on the vast and variable coastal zone of West Africa. One of the reasons for the limited number of tide gauges is the fact that the majority of the nearshore zone is composed by sandy environments, where these instruments are difficult to install and maintain, In this context spatial altimetry rises as the most adequate solution to overcome this problem. In this study we perform a demonstration of the use of satellite altimetry products to estimate local sea level trends. The study site selected for this work is the Cap Vert peninsula, Sen egal, and the tide gauge from Dakar was used to validate the sea level trends computed using altimetric sea level observations.

Ly, N.T.H. and Hoan N.T., 2018. Determination of nearshore wave climate using a transformation matrix from offshore wave data. In: Almar, R.; Almeida, L.P.; Viet, N.T., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 14–21. Coconut Creek (Florida), ISSN 0749-0208.

Nearshore wave climate is important for the assessment of coastal process and morphological changes. For port engineers, nearshore wave climate is crucial for the determination of operational conditions and downtime analysis. The nearshore wave climate is often derived by translation of the 10 to 30-year offshore time series to nearshore. Direct transformation of such large amount of observations is not feasible, since it requires an extremely long computational time. This paper describes an advanced technique to quickly derive nearshore wave conditions from offshore wave data. First, determination of matrix of boundary conditions in which matrix nodes are chosen to cover wave conditions at offshore boundary. Then, simulations of wave for each condition as described in the selected matrix of offshore conditions. The results are used to determine the matrix of wave conditions for any given nearshore location. This matrix consists of factors that specify the relation between the offshore (model forcing) and nearshore (model results) wave parameters. With this matrix, offshore wave observations can be translated to any nearshore location. With this technique, a 30-year long time series of offshore wave measurement can be rapidly (less than 2 days) translated to nearshore wave conditions. This paper discusses in detail the working principles of the technique, as well important aspects such as the optimization of boundary conditions matrix.

Thanh, T.M.; Tanaka, H.; Mitobe, Y.; Viet, N.T., and Almar, R., 2018. Seasonal variation of morphology and sediment movement on Nha Trang Coast, Vietnam. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 22–31. Coconut Creek (Florida), ISSN 0749-0208.

The Nha Trang beach, an embayed sandy beach located in the southeast of Vietnam, is a tropical touristic coastal environment that is being threat by persistent shoreline retreat. In order to investigate the processes underlying this erosive pattern, 1.5-years of video imagery, obtained from a local video system, was analyzed. Video products such as shoreline position and surf zone width (extracted from time-averaged images) were used to identify patterns of shoreline variability (using empirical orthogonal function – EOF) and investigate the link between the seasonal variations in the wave forcing and longshore sediment transport. Results indicate that shoreline retreat occurs essentially during the winter season, when energetic northeast monsoon waves dominate. The recovery phase (shoreline advance) was found to occur during the summer season, when milder south/southeast wind waves dominate. Shoreline variability was further investigated using EOF analysis and results show that the first mode, which explains 89% of the observed variance, corresponds to the seasonal longshore shoreline variations. This EOF mode was found to strongly related to the winter and summer monsoon seasons, thus reinforcing the role that seasonal changes in the wave climate play on the shoreline variations. Finally, the net of longshore sediment transport in Nha Trang beach was investigated using seasonal and monthly depth of closure (D_c) information, rather than a single fixed value of this parameter. The results highlight that the use of monthly or seasonal D_c values allow to capture the seasonal variations in the wave climate, thus providing more realistic patterns of sediment transport in this coastal area.

Duy, D.V.; Tanaka, H.; Mitobe, Y.; Anh, N.Q.D., and Viet, N.T., 2018. Sand spit elongation and sediment balance at Cua Lo Inlet in Central Vietnam. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 32–39. Coconut Creek (Florida), ISSN 0749-0208.

Erosion is significant on the downdrift beach of Cua Lo Inlet, which is located in Central Vietnam. The elongation of Cua Lo Inlet's updrift sand spit together with severe erosion of the downdrift bank is raising numerous social problems such as flood safety and land loss. In this study, a series of Landsat and Google Earth images were used to analyze and investigate the inlet recent morphological changes and evolution. Since 1970 the inlet has constantly migrated towards the sediment transport pathway, and its traveling distance has reached 1700 m. In order to quantitatively investigate such characteristics, the tip coordinates and the area of the sand spit updrift of the inlet were calculated. In particular, the area of the sand spit has increased remarkably, and the increasing rate is almost constant. Using this value, the rate of sand volume transported along the updrift sand spit by the waves was estimated and it is in good agreement with the longshore sediment transport rate of the surrounding beach.

Paniagua-Arroyave, J.F.; Correa, I.D.; Anfuso, G., and Adams, P.N., 2018. Soft-cliff retreat in a tropical coast: The Minuto de Dios sector, Caribbean coast of Colombia. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp 40–49. Coconut Creek (Florida), ISSN 0749-0208

Projections for the year 2100 predict a global mean sea level ~1 m above pre-industrial levels that will likely exacerbate coastal impacts worldwide and especially along vulnerable coastlines of developing countries. Recent studies have predicted a future shoreline retreat linked to the expected acceleration in global sea level rise along the soft-cliffs of Minuto de Dios on the Caribbean coast of Colombia. This study discusses previous results by arguing that an accurate quantification of relative sea level rise was not implemented and cliff retreat predictions are therefore not feasible. Future cliff-top positions and future sediment release were instead calculated by assuming that the historical retreat rate will remain unchanged. Mean end-point retreat between 1938 and 2010 was 1.7±0.4 m/year, which would produce between 2010 and 2060 a shoreline recession of 85 m with a cumulative release of ~530,000 m³ of sediment (for a ~ 1 km of ~ 6 m cliffs). The projected coastal retreat is expected to produce significant impacts to local infrastructure, including the loss of approximately 100 urban constructions. In addition, the 2060 coastline would be located ca. 50 m from the main road that connects Arboletes with the city of Montería. As discussed in this study, climate change-driven sea level rise will likely augment coastal hazards, but with limited data in the region, predictive modeling of future impacts remains speculative. This issue highlights the need for local stakeholders to dedicate resources to further observations. Such efforts will improve predictions, helping inform policy makers to implement successful local coastal management solutions.

Chien, N.Q. and Tung, T.T., 2018. Recent sedimentation of a mesotidal wave-dominated river mouth: Lach Van, Vietnam. In: Almar, R.; Almeida, L.P.; Viet, N.T., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 50–56. Coconut Creek (Florida), ISSN 0749-0208

The sedimentation of a wave-dominated river mouth in Tonkin Gulf, Vietnam, has been investigated for the time period 2005–2017. Deepwater wave statistics and the potential longshore sediment transport (LST) has been determined, which shows a net LST rate of ~10⁵ m³/yr southward. A one-line model is used to estimate the change in local coastline; the model is verified against shoreline position data obtained from satellite images. It is apparent that the accretion occurs on both sides of the river mouth with a rate of ~10 m/yr. Coastline evolution trend is then predicted for the aforementioned time period, and results show evidences that accretion is intensifying in recent years, which is most probably due to slight variation in local wave climate. Results of this study can be used as a scientific basis to propose solutions for stabilizing the river mouth entrance and its channel.

Thuy, M.T.T; Nagasawa, T.; Tanaka, H., and Viet, N.T., 2018. Sandy beach restoration using beach nourishment method: A case study of Nha Trang Beach, Vietnam. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp 57–66. Coconut Creek (Florida), ISSN 0749-0208.

Nha Trang Beach, located in the Northern part of Cam Ranh Bay, is famous as a tourist destination for its beautiful sandy beach. Since 1975, the Southern part of the beach has been considered a tourist hotspot where accommodation and business infrastructure are concentrated. However, in the past decade, severe erosion and shoreline retreat has occurred in the area. Human intervention in terms of house construction and other tourism infrastructure building is supposed to be one of main causes for these erosion problems. On the Northern beach, tourism demand is low despite its considerable potential. Between 2004 and 2005, a road was built on the Northern area, resulting in the loss of the beach, consequently affecting local tourism economy. The restoration of the sandy beach in this area is therefore crucial for local economic development. In this study, a concept of beach nourishment design for the Northern beach was proposed. Beach nourishment was designed for the purpose of bringing the shoreline back to the state of equilibrium it once had been before the road construction during 2004 – 2005. This study considered original equilibrium beach profiles, sediment grain sizes and wave climate characteristics in the design method of beach nourishment.

Wozencraft, J.; Dunkin, L.; Reif, M., and Eisemann, E., 2018. A spatial index approach to coastal monitoring: A Florida case study. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 67–75. Coconut Creek (Florida), ISSN 0749-0208.

Light Detection and Ranging (lidar) topography and bathymetry datasets and high-resolution aerial imagery have much to offer, but are typically very large, and efforts to extract information are often ad-hoc, leaving the full potential of high resolution airborne data unrealized. By developing methods for extracting and presenting consistent parameters and metrics applicable across coastal regions in the United States, this crucial information will become more readily available. Here, it is demonstrated how numerous geomorphological, navigation, and structural parameters are extracted from lidar topographic and bathymetric datasets. In addition, environmental parameters are extracted from hyperspectral imagery. Indices are developed from the extracted parameters to provide an evaluation of coastal engineering projects such as dredging and structures condition, as well as environmental projects including mitigation and restoration. A dashboard developed from the indices offers a clear and comprehensive presentation of coastal resource data products. Coastal condition as it relates to geomorphology, navigation infrastructure, and environmental considerations are presented using ‘stop-light’ symbology, providing a streamlined and easily interpreted illustration for decision making. The indices provide academia, industry, and government with repeatable, comprehensive coastal assessments that are regionally comparable allowing an integrated approach to management and planning in the coastal zone.

Kobashi, D. and Jose, F., 2018. Potential impacts of sand mining on hydrodynamics and fine sediment suspension and deposition on an inner-shelf shoal. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 76–85. Coconut Creek (Florida), ISSN 0749-0208.

Wave and hydrodynamic models are implemented to investigate whether sand mining on a transgressive sand shoal could influence hydrodynamic processes and sedimentary environment of the shoal covered with fine sediments. An effort is made to evaluating shoal hydrodynamic response to a hypothetical dredging scenario under a host of probable storm conditions. The model results show that changes in hydrodynamic and sedimentary environment strongly depend on the storm conditions and the shoal bathymetry. Wave dissipation, flow conditions and sediment re-suspension are significantly higher on the shallower western shoal and gradually decrease toward the deeper eastern section of the shoal. The finding suggests that the deeper eastern shoal can be exposed to frequent deposition of fine sediments, as opposed to the western shoal, despite its location farther away from the nearby major river mouth. It is concluded that large-scale sand mining, in particular from the shallower western shoal, is expected to profoundly alter the hydrodynamics and sediment suspension and deposition processes, which may also influence the benthic ecology of the shoal. The mining from the deeper eastern shoal may result in lesser impacts than the mining from the ecologically sensitive western shoal.

Appeaning Addo, K., 2018. Assessing ocean wave dynamics, potential sediment transport, and coastal erosion along Accra coast in Ghana. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 76–85. Coconut Creek (Florida), ISSN 0749-0208.

This study assessed wave dynamics and sediment transport along the coast of Accra in Ghana and compared the results with coastal erosion trend. Wave data from NOAA global wave model and measured buoy wave data were analysed as well as the potential sediment transport using the CERC's equation. The estimated mean significant wave height was 1.40 m and the period was between 10 and 15 seconds. The potential sediment transport rate was between 4.1 ×10⁵ m³/yr and 4.1 ×10⁵ m³/yr, while coastal erosion rate was 1.13 m/yr. Potential sediment transport rate increases from west to east. Coastal erosion is relatively high along the eastern and western coasts of Accra, while the central coast is relatively stable. Wave heights increased gradually from 1.00 m in January to a peak of 1.73 m in August, and eventually decreased to 1.10 m in December. The shape of the nearshore profile is significantly different along the eastern coast relative to the western and central coasts. This indicates that sediment transport intensity and nearshore bathymetry interaction in part explain the rate of erosion observed along the Accra coast in Ghana.

Scott, T.; Castelle, B.; Almar, R.; Senechal, N.; Floc'h, F., and Detandt, G., 2018. Controls on flash rip current hazard on low-tide terraced tropical beaches in West Africa. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 92–99. Coconut Creek (Florida), ISSN 0749-0208.

Flash rip currents are transient non-fixed offshore-directed jets of water often associated with migrating surf-zone eddies. They can occur on featureless (alongshore-uniform) beaches and are essentially hydrodynamically controlled. Due to their unpredictable nature, they represent one of the most significant hazards to bathers across surf zones worldwide, especially in Tropical West Africa, where high levels of flash rip activity and a lack of a lifeguard service lead to high drowning rates. Recent work has shed light on two contrasting driving mechanisms for non-fixed rips: (1) cascading vortices generated by wave breaking, and (2) shear instabilities of the longshore current. This research provides the first quantitative scientific understanding of wave-driven currents in Tropical West Africa. Specifically, the study focussed on the dynamics of flash rips occurring along alongshore-uniform beach morphology, through the collection of unique Lagrangian field measurements of flash rips. During two periods, February 2013 and March 2014, 13 days of field data collection occurred at Grand Popo beach on the southerly-facing Bight of Benin coast (Gulf of Guinea, West Africa). The experiments measured flash rip currents, nearshore hydrodynamics and morphology at a moderately energetic (long-term average significant wave height, Hs = 1.36 m, and peak wave period Tp = 9.4 s), sandy alongshore-uniform low-tide terraced beach exposed to South Atlantic groundswells and local wind-waves. A suite of GPS drifters, dye-tracking and video confirmed the presence and characteristics of low–high energy flash rips (up to 0.7 m/s) in the surf zone, while in-situ acoustic wave and current measurements from the surf zone and inner-shelf provided metocean forcing conditions (0.8<Hs<1.6 m; 8<Tp<14 s; 1°<Dp<21° (from shore normal)) and longshore current velocities (0.2–0.8 m/s in surf zone). Throughout a range of wave conditions (height/period/angle/directional-spreading) contrasting flash rip behavioural responses were observed (surf zone exits/offshore extent/offshore-directed velocities). This study (1) supports findings of the first rip experiment conducted at this site (Feb 2013) suggesting that flash rip activity is likely to be driven by wave breaking vorticity generation (flash rip activity high under shore-normal wave forcing) and (2) provides further quantitative insights into the role of specific wave/tide forcing characteristics on flash rip activity, specifically the importance of reduced directional spreading and tidal level in controlling increases in offshore extent of flash rip currents. Finally, (3) the observed ubiquity of significant hazardous transient flash rip activity and identification of key behavioural controls can provide a foundation for any future development of rip hazard prediction tools and effective lifeguarding in West Africa.

Floc'h, F.; Mabiala, G.R.; Almar, R.; Castelle, B.; Hall, N.; Du Penhoat, Y., Scott, T., and Delacourt, C., 2018. Flash rip statistics from video images. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 100–106. Coconut Creek (Florida), ISSN 0749-0208.

The coast of the Gulf of Guinea is exposed to high-energy waves generating strong nearshore currents both driving erosion and posing a threat to recreational beach goers and fishermen. Along this coast, the coexistence of swash and flash rip currents at Grand-Popo beach (Benin) was evidenced in a previous study using a limited number of Lagrangian drifter measurements. In this paper, a method based on color processing of video images from a permanent station has been developed to detect the presence of rip currents via a change of turbidity. Rip current characteristics and their link with tide and wave forcing over a 7-day period are derived. During this experiment, a total of 434 events has been counted during daylight. The majority of rips occurred at low tide and migrates downdrift. Flash rip activity is maximized for shore-normal wave incidence and mild wave conditions showing that flash rips are not driven by shear instabilities of the longshore current at this site. However, the lack of strong variability in wave forcing throughout the experiment prevents a more thorough wave-rip relationship investigation, which motivates the application of the method for a longer period with a wide wave-tide spectrum.

Floc'h, F.; Aziayibor, K.; Almar, R.; Du Penhoat, Y.; Lefebvre, J-P.; Dorel, M., and Delacourt, C., 2018. Origin of sediment fluxes in inner shelf zone via acoustic measurements, Grand Popo, Bénin. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 107–113. Coconut Creek (Florida), ISSN 0749-0208.

In the Gulf of Guinea, energetic swells generated in South Atlantic are responsible for one of the most important littoral drifts in the world, directed Eastward. The construction of harbour dams along this littoral disturbs the natural balance of the system and causes extreme erosion up to 10 m/year. Within the framework of this study, a serie of intensive measurements was conducted at Grand Popo from March, the 10^th to the 19^th, 2014. A large number of hydrodynamic, sedimentary and morphological parameters were measured. The backscatter signal from an Acoustic Doppler Current Profiler (ADCP) colocalised with a turbidity meter is inverted emprirically. Three main events of suspension over the whole water column are observed, during intense wind (>5m/s) lasting more than 8 hours. Actually, the water surface entrains after about 3–4 hours of intense wind, then the momentum is advected to the bottom in 2 or 3 hours depending on the intensity of the wind. The turbidity is then directly linked to the bottom stress derived from the mean current. The longshore flux is thus due to wind and always Eastward. The cross-shore flux is alternatively directed onshore or offshore. During spring tide, the offshore flux is in phase with the beginning of the tide flow. The exact origin of the current was not identified. Longshore flux were found to be 20 times higher than cross-shore flux.

Ngom, H.; Ndour, A., and Niang, I., 2018. Impacts of protective structures on sandy beaches: Example of the Saly balnear station, Petite Côte, Senegal. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal ofCoastal Research, Special Issue No. 81, pp. 114–121. Coconut Creek (Florida), ISSN 0749-0208.

Several protective structures have been built in recent years to protect sandy beaches of the seaside resort of Saly threatened by erosion processes. However, the protective seawalls, groynes and breakwaters have not produced the expected results. Erosion processes continue on the sandy coast of Saly. The shoreline evolution was estimated by two methods: a study of the evolution of the shoreline between 1989 and 2016 by the DSAS and a monthly monitoring in 2014 of a series of 8 beach profiles. The results show a considerable sedimentary imbalance between a northwestern sector generally in accumulation and a southeastern sector under erosion separated by the groyne of the Safary residence. The combination of different protective structures inhibits the manifestation of positive effects of some of them. In the southeastern sector, breakwaters slightly reduce the erosion rates of the beach which are still affected by the return flows associated with the groynes of northwestern sector. Riprap walls occupy recreational beaches and are subject to scour and submersion that make them unstable. All beaches just upstream of the groynes are generally in accretion. Beaches protected by newly constructed groynes are experiencing a remarkable accretion. All this shows that groynes are much more favorable than the breakwaters or seawalls for accretion on the sandy coast of Saly. A well-sized and structured groynes field that takes into account the physical and climatic characteristics of the coast could in the long term stabilize the sandy beaches of Saly.

Abessolo Ondoa, G.; Onguéné, R.; Tomedi Eyango, M.; Duhaut, T.; Mama, C.; Angnuureng, B.D., and Almar, R., 2018. Assessment of the evolution of Cameroon coastline: An overview from 1986 to 2015. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue. No. 81. pp. 122–129. Coconut Creek (Florida). ISSN 0749-0208.

The coast of Cameroon is located at the bottom of the Gulf of Guinea with varied nearshore environments and oceanic forcing influenced by the presence of several islands. It is also the area of important river flows. Here, the global evolution of the Cameroonian coastline and hydrodynamic between 1986 and 2015 is investigated using satellite images and ECMWF EraInterim re-analysis wave data. Seven areas of important cross-shore changes have been identified with only one case of human-induced variation that corresponds to the construction of a new habour at Kribi. This paper presents the results of using SYMPHONIE model with DOUALA26 configuration to assess the changes in Cameroon estuaries. The other areas are mainly located at the mouths of the rivers and at the entrance of Cameroon and Rio Del Rey esruaries. The results of the circulation model show that the convergence of Wouri, Dibamba river flows and littoral drift corresponds to the accumulation of sediments observed at “Souleyba”, while the eroded area at “Cap Cameroun” corresponds to the estuary output current. This work provides an understanding of erosive or accretive coastal processes using barotropic currents modeling in estuaries.

Hounguè, G.H.; Kounouhéwa, B.B.; Almar, R.; Sohou, Z.; Lefebvre, J-P.; Houépkonhéha, M., and Tokpohozin, B., 2018. Waves forcing climate on Bénin coast, and the link with climatic index, Gulf of Guinea (West Africa). In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 130–137. Coconut Creek (Florida), ISSN 0749-0208.

Bénin's coastline is currently undergoing very marked erosion. This erosion is the consequence of the impact of swells from the South Atlantic and is accentuated by human development. These swells, from weak to moderate energies, drive Bénin's coastline evolution. Although crucial, the characteristics of this forcing are not accurately defined. From instantaneous outputs of ERA40 and ERA-Interim's sea state parameters, the annual and seasonal average of significant wave height (Hs), peak period (Tp) and direction (Dir) were determined to characterize wave forcing and extreme event on Bénin Coast after a validation using the data of the ALIZEE buoy installed 6 km off the coast of Bénin in December, 2015. Hindcast data analysis indicates an important if increasing trend of Hs and Tp. A weak trend of peak direction towards the South West clockwise is observed between 1957 and 2016. The intra-annual variability of Hs shows a marked seasonality, the first one characterized by strong swells from April to October and the second one by moderate swells from October to April. Offshore wave height is positively correlated with AMO (Atlantic Multidecanal Oscillation).

Bonou, F.; Angnuureng, D.B.; Sohou, Z.; Almar, R.; Alory, G., and du Penhoat, Y., 2018. Shoreline and beach cuspsdynamics at the low tide terraced Grand Popo beach, Bénin (West Africa): A statistical approach. In: Almar, R.; Almeida, L.P.; Trung Viet, N., and Sall, M. (eds.), Tropical Coastal and Estuarine Dynamics. Journal of Coastal Research, Special Issue No. 81, pp. 138–144. Coconut Creek (Florida), ISSN 0749-0208.

This paper presents the description of a 2-dimensional shoreline and 3-dimensional shoreline behaviour around a ‘storm free’ microtidal beach from a 3-year video observation using empirical orthogonal function (EOF) analysis. The EOF method is applied successfully to delineate 2D and 3D developments that show the beach evolution influenced by the action of waves and tides. The EOF model results are in agreement with measurements that reflect the morphological concepts for the 2D and 3D cases: the first temporal EOF mode which accounts for an overwhelming 80% of shoreline variation reflects the alongshore-averaged cross-shore migration (2D) largely influenced by waves while the higher eigenfunctions with 20% shoreline variation reflect beach deformation/irregularities (3D). Shoreline location is correlated to cross-shore energy flow from waves, while 3D is associated to the longshore energy flow. The influence of wave height increases cross-shore uniform migration and beach seasonality. The results show that with EOF method, beach cusps are clearly identified for 3D developments to be evaluated. Beach cusps are well observed at low tides on video images. Tide and cusps increase the importance of short term events and deformation; at the lowest high tide mark, beach cusps were observed on higher spatial functions of EOF. This indicates that a study of these morphological features as a coupled system, promotes their contribution in predicting 2D and 3D shoreline changes.