Beach Profile Changes Research Articles

Experimental Analysis of the Changes in Coral Sand Beach Profiles under Regular Wave Conditions

This study utilized 50 laboratory experiments to document the evolution of coral beaches under varying regular wave conditions, including five distinct wave periods and ten wave heights. Both the type of equilibrium beach and the shape of sand bars were used to represent beach evolution. The evolution of coral sand beaches was then compared to quartz sand beaches. The experimental results show that the predicted (modeled) equilibrium profile of a quartz sand beach was not applicable to coral sand beaches. Compared to sand bars on quartz sand beaches, the distance from bar crests to the beach berm in coral sand beaches was greater, whereas the erosional depth of sand troughs was deeper. However, the grain size distribution of sand associated with the coral sand beach under wave action was consistent with Celikoglu’s law. Both an equilibrium beach profile classification model and a sand bar shape prediction model for coral sand beaches were developed based on the experimental data.

Simulating Erosive and Accretive Conditions in the Swash: Applications of a Nonlinear Wave and Morphology Evolution Model

This work presents a new model for surf and swash zone morphology evolution induced by nonlinear waves. Wave transformation in the surf and swash zones is computed by a nonlinear wave model based on the higher order Boussinesq equations for breaking and non-breaking waves. Regarding sediment transport, the model builds on previous research by the authors and incorporates the latest update of a well-founded sediment transport formula. The wave and morphology evolution model is validated against two sets of experiments on beach profile change and is afterwards used to test the performance of a widely-adopted erosion/accretion criterion. The innovation of this work is the validation of a new Boussinesq-type morphology model under both erosive and accretive conditions at the foreshore (accretion is rarely examined in similar studies), which the model reproduces very well without modification of the empirical coefficients of the sediment transport formula used; furthermore, the model confirms the empirical erosion/accretion criterion even for conditions beyond the ones it was developed for and without imposing any model constraints. The presented set of applications highlights model capabilities in simulating swash morphodynamics, as well as its suitability for coastal erosion mitigation and beach restoration design

Study of Beach Profile Change and Prediction for Maritime Construction

Study of Beach Profile Change and Prediction for Maritime Construction

TEST OF LSTM NETWORKS IN LONG-TERM BEACH MORPHOLOGICAL CHANGES

In the prediction of beach profile changes, for example, the long-term calculation of daily changes can only provide sufficiently reliable reproduction results for a few years. One of the reasons is that actual morphological change is caused by the superposition of complex processes that are unknown. The prediction of timeseries data by data-driven models in contrast to physical models has been applied to various fields in recent years with the spread of deep learning and is expected to be used as a tentative solution for problems that cannot be adequately predicted by physical modeling. Recurrent neural networks are being applied to predict shoreline change over several years (Montaño et al., 2020), but application to spatial morphological changes, such as beach profile changes, is rarely investigated due to the limitations of the large amount of observation data required for learning. Here, we used the LSTM (Long Short-Term Memory) network, one of the recurrent neural networks, and long-term beach profile data observed at the Hasaki coast, Japan for learning and prediction of beach profile changes.

CROSS-SHORE BEACH PROFILE SIMULATION IN THE SWASH ZONE OF NARRABEEN-COLLAROY BEACH

Sediment transport and, consequently, the beach profile changes in the swash zone are important to the overall sediment budget and beach profile evolution because the hydrodynamic condition in this zone is complex. One of the swash zone morphodynamic difficulties is estimating the beach profile accretion and erosion above the mean water level. Although there have been considerable studies and investigations into the swash zone morphodynamic, numerical models for predicting sediment transport rate and beach profile changes are limited. Therefore, this study examined a morphodynamic numerical model to predict beach profile evolution in the swash zone using a nearshore beach profile dataset measured at the Narrabeen-Collaroy beach, Australia.

Numerical Simulation of the Beach Response Mechanism under Typhoon Lekima: A Case Study of the Southern Beach of Chudao

Typhoons play an important role in beach evolution. The storm surge and large waves caused by typhoons can cause significant changes in beach morphology in a short period of time. The mechanism of beach evolution and profile changes during typhoons is significantly different from that under non-typhoon dynamic conditions. The XBeach numerical model provides an effective tool for predicting the response of sandy coasts to typhoons. This study is based on field-collected long-term beach profile elevations and grain size data, which were used to establish a two-dimensional XBeach model for simulating the morphological evolution of Cudao Island Beach under Typhoon Lekima. The GSA (Generalized Sensitivity Analysis) method was used to determine the sensitivity order of several important parameters in this modeling. Four different moments of wave height variation were selected during the typhoon process to analyze and study beach evolution. The results show that Chudao South Beach is always in a state of erosion during the typhoon period. The wave water increase is apparent in the nearshore wave-breaking area. The beach shoulder in the northeastern part of the beach is short, and the profile, with a short length, responds quickly to the typhoon. The eroded sediment is mainly deposited in the lower part of the intertidal zone or even transported outside of the wave-breaking zone, and a small part is transported to the shore and deposited in the high-tide zone. The continuous sediment transport along the coast of Chudao Beach is an important factor that influenced the evolution of each profile during Typhoon Lekima.

Sandy beach dynamics by constrained wave energy minimization

This paper focuses on a new approach to describe coastal morphodynamics, based on optimization theory, and more specifically on the assumption that a sandy beach profile evolves in order to minimize a wave-related function, the choice of which depends on what is considered the driving force behind the coastal morphodynamic processes considered. The numerical model derived from this theory uses a gradient descent method and allows us to account for physical constraints such as sand conservation in wave flume experiments. Hence, the model automatically adapts to either wave flume or open sea settings and only involves two hyper-parameters: a sand mobility and a critical angle of repose. The ability of OptiMorph to model cross-shore beach morphodynamics is illustrated on a flume configuration. Comparison of the beach profile changes computed with OptiMorph with experimental data as well as the results from the coastal morphodynamic software XBeach demonstrates the potential of a model by wave energy minimization.

Geomorphological response of sandy beach to tropical cyclones with different characteristics

Tropical cyclones (TCs) play important roles in the evolution of beaches. The response of beaches to a single tropical cyclone (TC) has been well reported, however, few studies have compared the responses of the same beach to TCs with different characteristics. Taking Haiyang Beach in the northern China Seas as a case study, the beach profiles before and after two TCs, Lekima and Bavi, which passed through the west and east sides of the study area, were investigated. The beach exhibited erosion at the upper foreshore and minor deposition near the mean high water level (MHW) after Lekima with subaqueous sandbars formed in the nearshore zone, whereas all the beach profiles showed little changes after Bavi. A high-resolution FVCOM model was established and eleven sensitive experiments were conducted to simulate hydrodynamic changes induced by TCs with different tracks, intensity and duration. Then the Xbeach model was used to display the beach evolution due to different TCs conditions. It is found that the significant storm surge and strong seaward bottom current induced by landward wind of the TCs passed through the west side of the study area should responsible for the beach profile changes. Negligible storm surge rise and landward bottom current related to the seaward wind of eastern path TCs can only result in little change of the beach. Swell contributes most to the wave height while has less effect on the beach changes. In this study, we conclude that the effects of TCs on beaches are primarily dependent on relative position of a beach and TCs’ tracks.

Beach profile changes induced by surrogate Posidonia Oceanica: Laboratory experiments

New flume experiments with surrogate seagrass meadows are presented. The experiments included the creation of a full-scale and realistic Posidonia Oceanica model to evaluate the effect over wave attenuation, sediment transport and shoreline erosion. A hydrodynamic and morphodynamic comparison between cases with seagrass and without seagrass for two wave energy conditions was performed. Meadow density and submergence ratio were constant for tests under irregular waves. The wave height reduction, bar crest location, total sediment transport and shoreline position were used to evaluate the coastal protection efficiency of the meadow. The measured wave heights suffered a reduction due to the presence of the seagrass. These reductions were persistent in the area located between the onshore edge of the meadow and the depth of closure, being of greater magnitude in the more energetic case. All tests showed the development of a bar and the migration of the crest offshore over time. However, the dissipation of the incoming wave energy on the meadow made the bar crest stay closer to the shoreline and consequently generated a lower freeboard. In addition, the bar migration rate was reduced by the simulated meadow effect, in particular in the lower energetic case. A sediment volume significantly smaller was transported offshore when the seagrass meadow was present in both wave conditions. Additionally, in the higher energy case, a smaller shoreline retreat was observed when the meadow was present. • Flume experiments were carried out with a realistic Posidonia Oceanica model to assess the effect on beach sediment transport. • Two wave condition were analysed comparing the test with and without seagrass meadows. • Wave heights were reduced due to the effect of the Posidonia Oceanica model in areas after the meadow. • The total volume of sediment transported in the seagrass meadows cases was considerably less than without seagrass meadows. • Bar crest morphological parameters and shoreline position were analysed to verify the meadow effect on the coastal protection.

Influences of beach berm height on beach response to storms: A numerical study

The field observation at two neighboring beaches showed significant effects of berm height on beach profile changes during a major storm. The fully nonlinear Boussinesq wave model, FUNWAVE-TVD, with a sediment transport module was used to simulate the beach erosion processes of the two beaches. The model reproduced the beach profile changes in good agreement with the measured data. The model results revealed that, for the beach with a higher berm, the wave force, wave-induced undertow flow, along with the higher sediment concentration on the berm induce more offshore sediment transport and cause significant beach profile changes compared to the beach with a lower berm. The erosion trend with different berm heights was predicted by using a series of numerical tests with different berm heights and offshore forcing conditions. The test results suggested that beach erosion increases with the berm height until the berm height reaches a certain level.

Effects of beach width variability on recreational function: A case study of NE Brazil

Beaches have historically been recognized as one of the main spaces for leisure and recreation for residents and tourists worldwide. They are maintained by the combined action of waves, tides, currents, and winds that directly affect their composition, shape, and size. Subject to morphological variations on a short-term scale (hours and days) as a result of the action of storm waves or extraordinary tidal events, the geomorphic and sedimentary characteristics of the beach are important for determining recreational function. Considering that the beach profile changes seasonally owing to the conditions of sea agitation and sand supply, some uses may not adapt to these variations. Thus, there must be a minimum beach width for recreational functions to be developed. The method used to measure beach width is an important parameter to study erosion and accretion on beaches around the world. However, the detection of long-term changes in beach width is challenging because it is necessary to have observational data on the beach morphological change. In this study, we evaluated the relationship between the variability of the width of the emerged beach and its effects on recreational function in a stretch of Tabuba beach, Caucaia, Ceará.

Importance of Beach Evaluation for Integrated Coastal Zone Management

Coastal erosion and accretion are short-term and long-term processes that may cause changes in shoreline and beach profiles. Monitoring beach profile is important to figure out the factors that are responsible for these changes so it helps the stakeholders in planning sustainable beach management that plays a vital role in achieving Integrated Coastal Zone Management (ICZM). For this reason, a beach survey was conducted at the study area to monitor and determine the factors that led to erosion and accretion on beach profile. DEM (Digital Elevation Model) helped on comparing between the elevations of ground control points through four seasons of the survey, which compensated: November 2020, December 2020, February 2021, April 2021 and July 2021. The used methodology of using GPS (Global Positioning System) depended on stop and go methodology within the two locations in the study area: site A (Jal El Bahr north of Tyre) and site B (Bahr Slaiyeb south of Tyre). GIS (Geographic Information System) is another tool that was used to have LC (land cover) map. Meteorological data was extracted from Saksakye weather station north of Tyre. Results of beach survey indicated that the two study areas were exposed to change on profile through the study period especially at Bahr Slaiyeb. These changes in the two study areas are a result of anthropogenic pressure (grooming and cleaning, grazing, human trampling, construction, etc..), vegetation cover and meteorological factors (wind speed, wind direction and precipitation). This database could be used to support in outlining the baseline of strategic beach monitoring and ICZM.

Littoral drift analysis based on long-term observation of mesotidal beach profile in Kuta Beach, Bali for coastal retreat assessment

The beach profile survey in the intertidal zone is crucial for a temporal variability study of shoreline and beach profile change for coastal management. The combination of numerical modelling and field data has proven to be successful in identifying the primary hydrodynamic and sediment transport processes such as littoral and cross-shore drift. Those parameters are relevant to the sandbar migration process and shoreline changes. The purpose of the present study is to analyse the littoral drift that caused temporal variability shoreline change in mesotidal beach for coastal retreat mitigation. Beach profile data of Kuta Beach was analyzed by 7 years of long-term field observation data both east monsoon and west monsoon situation. The shoreline definition used mean sea level (MSL)1.3 m and high water level (HWL) 2.6 m as reference. By using the MeEPASoL program as a graphical user interface program, shoreline changes converging to an equilibrium state can be simulated by taking into account the existing breakwater. Temporal shoreline position resulting from littoral drift and beach width change from its initial position is estimated for coastal erosion analysis. The result showed that dominantly, the littoral drift pattern moved from south to north. Furthermore, this study can be used in the process of identifying the primary hydrodynamic analysis in erosion disaster management as assessment of the beach erosion.

Evaluating XBeach performance for extreme offshore-directed sediment transport events on a dissipative beach

ABSTRACT The performance of the process-based nearshore model XBeach for predicting extreme offshore-directed sediment transport was investigated using field observations at a dissipative beach in Japan. Three extreme erosion events were identified from a record of 6,209 observations of the cross-shore profile change at Hasaki, Japan, from 1987 to 2003. The analysis considered the sensitivity of the wave nonlinearity of short waves that could be tuned using the parameter, fua , to the observed bed profile change. The comparisons revealed that for extreme offshore-directed sediment transport events, fua = 0.0 is the best fit for predicting these extreme beach profile changes. In the nearshore zone, erosion was underestimated, and the BSS exhibited low values. Peak sediment deposition occurred in the bar-offshore zone with sediments transported from the nearshore zone and was estimated by the model reasonably well. In addition to the three extreme events, 14 other large events were identified, and the trends of beach profile change could be estimated with sufficient tuning of the fua parameter. After analyzing the correlation between fua and wave and morphology-related parameters, the fua value could be correlated to the observed volume change. This suggested that if there were a rough estimate of the expected total volume change, this may help in setting fua value.

Statistical analysis of beach profiles – A spatiotemporal functional approach

Beach profile data sets provide valuable insight into the morphological evolution of sandy shorelines. However, beach monitoring schemes often show large variability in temporal and spatial intervals between beach profiles. Moreover, beach profiles are often incomplete (i.e. only a part of the profile is measured) and data gaps are unavoidable. The resulting irregular sets of beach profiles complicate statistical analysis and previous studies on the morphological evolution and the effects of external influences have often omitted incomplete beach profiles. In this perspective, a statistical model is suggested to study beach profiles and to identify the effects of external influences. To be precise, the statistical model can be used (1) to determine the temporal and spatial variability of beach profiles while accounting for autoregressive dependencies in space and time, (2) to identify effects of external influences, (3) to predict complete beach profiles at unknown locations (i.e., interpolation between beach profiles), and (4) to forecast complete beach profiles accounting for external influences, such as storm events or nourishments. To illustrate the applicability of this model to irregular beach profile data, this state-of-the-art functional, spatiotemporal model was applied to beach profiles of the island of Sylt, Germany. In a first case study on submerged beach profiles, a decreasing temporal dependency between the profiles in the offshore direction was revealed, highlighting that less frequent measurements of offshore areas would suffice. A second analysis of the emerged beach profiles revealed the general effect of storm conditions (wave heights > 5 m) on subsequently measured beach profiles, which was statistically significant, and the profiles eroded with approximately 0.2–0.7 m in height. In summary, this study proposes and explores the application of a state-of-the-art statistical model to investigate beach profile changes from increasingly diverse and large profile data in coastal engineering and management.

High-resolution, large-scale laboratory measurements of a sandy beach and dynamic cobble berm revetment

High quality laboratory measurements of nearshore waves and morphology change at, or near prototype-scale are essential to support new understanding of coastal processes and enable the development and validation of predictive models. The DynaRev experiment was completed at the GWK large wave flume over 8 weeks during 2017 to investigate the response of a sandy beach to water level rise and varying wave conditions with and without a dynamic cobble berm revetment, as well as the resilience of the revetment itself. A large array of instrumentation was used throughout the experiment to capture: (1) wave transformation from intermediate water depths to the runup limit at high spatio-temporal resolution, (2) beach profile change including wave-by-wave changes in the swash zone, (3) detailed hydro and morphodynamic measurements around a developing and a translating sandbar.

Effect of Erosion and Accretion on Beach Profile in Kuala Terengganu Coastal Areas

Coastal erosion and accretion are long-term process that may cause changes in shoreline and beach profiles. Due to erosion and accretion effects, most of the coastal areas in Malaysia are suffering from destruction of property especially at the coastal areas in east coast of Peninsular Malaysia. This study was conducted to determine the effects of erosion and accretion on beach profiles at four (4) coastal areas in Kuala Terengganu using remote sensing and GPS observation methods. The objectives include to derive the coastal erosion and accretion rate, to measure coastal elevation for beach slope angle calculation, and to determine the relationship between beach slope angle with coastal erosion and accretion. The erosion and accretion rate was derived from SPOT-5 satellite image and unmanned aerial vehicles (UAV). In order to obtain the beach profile, the elevation with 50m offset for every chainage, and 5m offset for each cross-section point were carried out using real-time kinetic (RTK) observation methods. It was found that the highest and lowest erosion and accretion rates were 170.29 m²/year and 57.53 m²/year, respectively. The beach profile became steeper with the beach slope values of 11.004° and 7.652° at high and low erosion areas, respectively. The relationships between beach slope angle and coastal erosion/accretion were found as 0.12 and 0.86 respectively. The findings showed that steeper beach profiles influenced the high rate values of erosion and accretion. For more accurate findings, further studies on the factors affecting the erosion and accretion such as monsoon seasonal changes and morphological impact are necessary to support the reliable decision-making process for sustainable coastal management.

A New Beach Topography-Based Method for Shoreline Identification

The definition of shoreline is not the same for all contexts, and it is often a subjective matter. Various methods exist that are based on the use of different instruments that can determine and highlight a shoreline. In recent years, numerous studies have employed photogrammetric methods, based on different colours, to map the boundary between water and land. These works use images acquired by satellites, drones, or cameras, and differ mainly in terms of resolution. Such methods can identify a shoreline by means of automatic, semi-automatic, or manual procedures. The aim of this work is to find and promote a new and valid beach topography-based algorithm, able to identify the shoreline. We apply the Structure from Motion (SfM) techniques to reconstruct a high-resolution Digital Elevation Model by means of a drone for image acquisition. The algorithm is based on the variation of the topographic beach profile caused by the transition from water to sand. The SfM technique is not efficient when applied to reflecting surfaces like sea water resulting in a very irregular and unnatural profile over the sea. Taking advantage of this fact, the algorithm searches for the point in the space where a beach profile changes from irregular to regular, causing a transition from water to land. The algorithm is promoted by the release of a QGIS v3.x plugin, which allows the easy application and extraction of other shorelines.

Comparative Analysis of the Erosion Mechanism of Different Profiles in the Arcuate Foreshore under Typhoon Action

The comparison results of three beach profile data repeatedly measured before and after the typhoon in Shuidong Bay, west Guangdong province which show that there are significant differences in beach profile erosion and response process. And the changes of beach profile can be divided into: strong downward overall low shoreline regressive type and overall slight erosion shoreline regressive type. Application of the modified mild-slope equation along three beach profile are simulated wave high reflection to the sea side, to the section vertical shore pressure gradient and including water roll force and radiation stress, the vertical shore forces one dimensional profile along the momentum conservation equation (radiation stress and water roll force) bottom friction and lateral mixing reaction between numerical solution, the momentum conservation equations of the wave increases the water flow velocity and section along the profile distribution of wave height and related forces. The analysis shows that the extent and difference of coastal erosion depend on the shoreline erosion mode stimulated by the maximum surge water of the coastal current and the maximum velocity of the coastal current and the dynamic state of the profile topography under the action of the profile location, morphology and incident wave elements.

Laboratory investigation of coastal beach erosion processes under storm waves of slowly varying height

Storm-induced large coastal waves are a predominant driver for coastal erosion problems, but the physical processes of storm erosion have not been fully understood due to some technical difficulty in simulating storm waves with timely varying heights in the laboratory and collecting storm beach profiles in the field. In this study, novel series of experiments are proposed to study sandy beach processes under coastal storm conditions in a laboratory wave flume of 60 m long, 3 m wide and 1.5 m high. Two water depths of h = 0.5 m and h = 0.7 m were used to investigate beach response under low and high tidal levels. Two initially uniform plane beach slopes of tanβ=1/15 for dissipation beach and tanβ=1/5 for reflection beach were used to study beach profile changes. Additionally, intermediate beach tanβ=1/10 was also experimentally investigated under regular waves in another wave flume of 30 m long, 0.6 m wide and 1 m high. Non-intrusive instrumentation of high-resolution cameras was used to record time-series photo images on beach profile evolution in spatial resolution of 0.2 cm and a temporal resolution of 0.1 s. Image analyzing techniques were also developed to transform the recorded photo images to digital data on both beach and water-surface profiles. In analyzing the collected data, it is found that the variation of storm wave height results in changes of wave breaking point and also sediment transport direction before and after the wave breaking point. Sediment transport direction was found to move onshore initially under small storm waves, and then a sand-bar was generated and a certain portion of sediment also moved offshore under large waves, but such monotonic relationship between sediment transport and wave forcing could transform as morphology feedback and phase lags between wave orbital fluid velocity and sediment concentration. The wave energy flux at the breaking point is shown to be suitable parameter in predicting beach mass change or storm erosion rate, while the dimensionless sediment settling velocity parameter Ω′ may not be a suitable criterion for predicting beach erosion or accretion under storm waves.