Beach Profile Research Articles

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, Water Level, and Wave Runup Measurements Using a Standalone Line-Scanning, Low-Cost (LLC) LiDAR System

A prototype rapidly deployable, Line-scanning, Low-Cost (LLC) LiDAR system (USD 400 per unit; 2020) was developed to measure coastal hydro-morphodynamic processes. A pilot field study was conducted at the U.S. Army Corps of Engineers, Field Research Facility (FRF) in Duck, North Carolina, USA to evaluate the efficacy of the LLC LiDAR in measuring beach morphology, wave runup, and free-surface elevations against proven approaches. A prototype LLC LiDAR collected continuous cross-shore line scans for 25 min of every half hour, at ~7 revolutions/s and ~1.3° angular resolution, at two locations (one day at each location), spanning 12 m (i) on the backshore berm (35 scans; Series B) and (ii) in the swash/inner surf zone (28 scans; Series C). LLC LiDAR time-averaged beach profiles and wave runup estimates were compared with the same quantities derived from the continuously sampling terrestrial LiDAR scanner installed atop the dune at the FRF (DUNE LiDAR). The average root-mean-square difference (RMSD) between 17 (6) time-averaged LLC and DUNE LiDAR beach profiles was 0.045 m (0.031 m) with a standard deviation of 0.004 m (0.002 m) during Series B (Series C). Small-scale (cm) swash zone bed level changes were resolved over 5-min increments with the LLC LiDAR. The RMSD between LLC- and DUNE LiDAR-derived wave runup excursions over two 25-min segments was 0.542 m (cross-shore) and 0.039 m (elevation) during the rising tide and 0.366 m (cross-shore) and 0.032 m (elevation) during the falling tide. Between 72–79% of the LLC LiDAR wave runup data were more accurate than the RMSD values, thereby demonstrating the LLC LiDAR is an effective, low-cost instrument for measuring wave runup and morphodynamic processes. Co-located water levels were measured with a continuously sampling (16 Hz) RBRsolo3 D|wave16 pressure logger during Series C. LLC LiDAR free-surface elevations at the nadir during one high tide (4.5 h) compared well with pressure-derived free-surface elevations (RMSD = 0.024 m, R2 = 0.85).

Coastal Geomorphology and Geospatial Beach Profile Assessment for East Coast Monsoonal Coastlines.

The main concern for this research is slope estimation and the beach profiling with verification sensor-based remotely data (high spatial resolution). Thus, surveying and satellite extraction data need to be accurat. It had been proven to support the relationship between coastal erosion with beach slope changes along Kuantan, Pahang. Therefore, the actual coastline can be mapped from last vegetation features and determine physical condition of beach on coastal habitable land where the baseline has been changes due to sea-level rise event. Hence, the aim of this study is to monitor beach profile using high spatial resolution remote sensing imagery and GIS techniques to distinguish slope estimation from different sources in Kuantan, Pahang Site-verification are done to identify beach slope profiling along Kuantan coastline, Pahang. The objectives of this research are i) to generate coastal slope estimation and beach profile in year 2006 and 2014, ii) to quantify the estimated and observed beach slope from IFSAR data and slope site surveying (by NAHRIM) and iii) to visualise in 3-D view of coastal slope profile derived using IFSAR data. The accuracy values provided for the measurements made in open area, undisturbed area with slopes less than 10 %. From early reconnaissance of Kuantan beach, most of the area are flat and sandy profile to which are suitable for this application. Besides, we found out this method are reliable to produce appropriate slope profile along identified areas in selected Pahang coastline. The findings may indicated a better strategy for monitoring coastline changes is needed especially for vulnerable coastal erosion areas for future sustainable coastal management.

Analysis of the mechanics of breaker bar generation in cross-shore beach profiles based on numerical modelling

In this work, a recently developed numerical model, capable of solving the hydro- and morphodynamics of the cross-shore beach profile, is used to gain insight into the relevant processes driving the generation of a breaker bar. The bedload and suspended sediment transport contributions are analysed separately. It has been shown that the bedload transport tends to accumulate sediment on the onshore side of the undertow detachment point, at a distance that depends on the skewness of the waves and the magnitude of the friction velocity, shaping the onshore face of the breaker bar. In contrast, the suspended transport contributes to the growth of the offshore side of the breaker bar. Besides, a comparison between the sediment transport rates produced by different types of breakers shows a faster bathymetric evolution and an offshore displacement of the position of the breaker bar for high Iribarren numbers. Differences are consistent with the proposed mechanisms driving the evolution of the beach profile. The findings of this work provide a better understanding of the processes driving the formation of breaker bars, how they interact with each other and the relative importance of bedload and suspended sediment transport at each location of the cross-shore profile.

Shoreline Evolution and Erosion Vulnerability Assessment along the Central Adriatic Coast with the Contribution of UAV Beach Monitoring

Coastal erosion and its impacts on the involved communities is a topic of great scientific interest that also reflects the need for modern as well as cost and time-effective methodologies to be integrated into or even to substitute traditional investigation methods. The present study is based on an integrated approach that involves the use of data derived from UAV (Unmanned Aerial Vehicle) surveys. The study illustrates the long- to short-term shoreline evolution of the Molise coast (southern Italy) and then focuses on two selected beach stretches (Petacciato and Campomarino beaches), for which annual UAV surveys were performed from 2019 to 2021, to assess their most recent shoreline and morpho-topographical changes and related effects on their coastal vulnerability. UAV data were processed using the Structure from Motion (SfM) image processing tool. Along the beach profiles derived from the produced DEMs, the coastal vulnerability of the selected beach stretches was evaluated by using the Coastal Vulnerability Assessment (CVA) approach. The results obtained highlight some significant worsening of CVA indexes from 2019 to 2021, especially for the Campomarino beach, confirming the importance of the periodic updating of previous data. In conclusion, the easy use of the UAV technology and the good quality of the derived data make it an excellent approach for integration into traditional methodologies for the assessment of short-term shoreline and beach changes as well as for monitoring coastal vulnerability.

Data related to "Influence of the Initial Beach Profile on the Sediment Transport Processes during Post-storm Onshore Bar Migration."

Data related to "Influence of the Initial Beach Profile on the Sediment Transport Processes during Post-storm Onshore Bar Migration."

Holocene sea-level rise and coastal aquifer interactions: Triggering mechanisms for environmental change and impacts on human settlement patterns at Dor, Israel

Future sea-level rise is expected to affect coastal aquifers and environments and have significant impacts on coastal communities. Here, we describe the impact of early to late Holocene sea-level variations on the coastal environment and human settlements of the Carmel Coast, Israel. One of these ancient communities, Tel Dor, was settled initially during the Late Pottery Neolithic (ca. 7 ka) on a wetland surface and then abandoned for ca. 1.5 ka before resettlement occurred on the adjacent aeolianite ridge from the Middle Bronze Age to the Crusader period (4.3–0.9 cal Ka BP). For the first time, high resolution chrono-bio-chemo-stratigraphy of sediment cores collected landward of the current shoreline at Dor are presented capturing a record of poorly sorted sand mixed with marine shells, well sorted aeolian sand and silty clay deposits. The record represents a series of brackish-freshwater wetlands formed in the coastal area of Dor between ca. 15 to 7 ka in response to relative sea-level rise and resulting rise of the coastal aquifers. After 7 ka, due to rising sea level and a transgressing shoreline, sand largely derived from the Nile Delta, reached the coast including the coastal wetland. Landward from the current shoreline, the period between ca. 7 to 4 ka is represented by alternating sand-silt facies consisting of reworked marine shells and brackish-fresh water biota. These lithological cycles reflect fluctuations between coastal and wetland environments governed by the response of the coastal aquifer to sea-level rise. Rapid sea-level rise led to a rise in the groundwater table and inundation of the area around Tel Dor, while periods with slower rates of sea-level rise resulted in coastal sand deposition. The settlement gap at Dor between 7 and 5.6 ka possibly reflects the behavioral response of the coastal settlers to sea-level fluctuation, and sediment depositional variation instigating aquifer inundation coastal marsh development and mobilization of sand bodies. This study provides a record of beach profile build-up along the Mediterranean coast of Israel and serves as an example of how sea-level rise affect unconfined coastal aquifers and the formation of wetlands due to rising water tables in low elevation coasts. Coastal inundation is a long-term risk factor for densely populated low-lying coastal regions that require a proactive approach for solving cascading impacts of sea-level rise.

Experimental Investigation on the Mechanism of Longshore Sediment Transport Using a Circular Wave Basin

In this paper, a hydraulic model experiment was conducted to investigate the mechanism of longshore sediment transport on a sloping beach of 1:7 using a circular wave tank equipped with a spiral wave maker. The experimental results revealed that cross-shore sediment transport was predominant up to the formation of equilibrium cross-section. Then the longshore sediment transport was actively dominant near the bar after the development of equilibrium topography. The wave-breaking positions and the characteristics of sand displacement in the vicinity of the wave-breaking zone were observed throughout the installation of fluorescent sands in different cross-sections under several wave conditions on the same terrain to presume the coastal erosion. From the outcomes, it was confirmed that the gradient of the average water level due to the obliquely incident waves breaking and the differences in breaking positions along the shoreline accelerated the generation of longshore currents and longshore sediment transport in the sloping beach profile. Moreover, the actively longshore sediment transport tendency throughout the breaking waves and the longshore current had been confirmed in this study where the gradually increasing wave heights influenced the stronger degree of wave breaking on the sloping beach, which enhanced the sediment transport procedure to deform the beach profile.

Subaqueous and Subaerial Beach Changes after Implementation of a Mega Nourishment in Front of a Sea Dike

Sandy nourishments can provide additional sediment to the coastal system to maintain its recreational or safety function under rising sea levels. These nourishments can be implemented at sandy beach systems, but can also be used to reinforce gray coastal infrastructure (e.g., dams, dikes, seawalls). The Hondsbossche Dunes project is a combined shoreface, beach, and dune nourishment of 35 million m3 sand. The nourishment was built to replace the flood protection function of an old sea-dike while creating additional space for nature and recreation. This paper presents the evolution of this newly created sandy beach system in the first 5 years after implementation based on bathymetric and topographic surveys, acquired every three to six months. A significant coastline curvature is created by the nourishment leading to erosion in the central 7 km bordered by zones with accretion. However, over the five-year period, net volume losses from the project area were less than 5% of the initial nourished sand volume. The man-made cross-shore beach profile rapidly mimics the characteristics of adjacent beaches. The slope of the surfzone is adjusted within two winters to a similar slope. The initially wide beaches (i.e., up to 225 m) are reduced to about 100 m-wide. Simultaneously, the dune volume has increased and the dune foot migrated seaward at the entire nourished site, regardless of whether the subaqueous profile gained or lost sediment. Our results show that the Hondsbossche Dunes nourishment, built with a natural slope and wide beach, created a positive sediment balance in the dune for a prolonged period after placement. As such, natural forces in the years after implementation provided a significant contribution to the growth in dune volume and related safety against flooding.

Wave overtopping at near-vertical seawalls: Influence of foreshore evolution during storms

This work presents the results of an investigation on how wave overtopping at a near-vertical seawall at the back of a sandy foreshore is influenced by sequences of erosive storms. The experiments were carried out in the Large Wave Flume (GWK) at Leibniz University, Hannover (Germany). The tested layout consisted of a near-vertical 10/1 seawall and a sandy foreshore with an initial 1/15 slope. Three sequences of idealised erosive storms were simulated. Within each storm both the incident wave conditions and still water level were varied in time to represent high and low tide conditions. Each sequence started from a 1/15 configuration and the beach was not restored in between storms. The measurements included waves, beach profile, wave overtopping volumes. The profile of the beach was measured after each sea state tested.Wave overtopping at each stage of the tested storms was significantly influenced by bed changes. This was linked to the measured evolution of the beach. Measurements showed that a barred profile developed quickly at the start of each sequence, and scour developed at the toe of the structure during high water level conditions, while accretion or partial backfilling developed during low water level conditions. Due to these processes, the position of a sea state in the tested sequence is shown to be an important factor in determining the wave overtopping volume. Remarkably, when a weaker idealised storm followed a more energetic one, nearly the same level of overtopping was recorded. This is explained by the foreshore erosion, leading to increased water depths and wave heights at the toe of the structure. This finding allows to quantify and to explain the variability of wave overtopping in storms following one another at intervals shorter than the recovery time of the foreshore.

A machine-learning hybrid-classification method for stratification of multidecadal beach dynamics

Coastal areas are one of the most threatened natural systems in the world. Environmental beach indicators, such as erosion and deposition rates of exposed beaches in Andalusia (640 km), were calculated using the upper limit of the active beach profile and detailed orthophotos (1:2500) for the periods 1956–1977, 1977–2001 and 2001–2011. A hybrid classification method, both supervised and unsupervised, based on machine-learning (ML) techniques was then applied to model beach response and dynamics for this 55-year period. The use of a K-means technique allowed stratification into four beach groups that have responded similarly in terms of coastline mobility and erosion/deposition patterns. Furthermore, the application of a classification and regression tree (CART) based on the K-means results helped to identify the threshold values for erosional and depositional rates and the period that characterises each cluster or stratum, enabling correct classification of 1415 out of 1509 beaches (93.77%).

Emulator For Eroded Beach And Dune Profiles Due To Storms

AbstractDunes and beaches are vulnerable to erosion during storm events. Numerical models can predict beach response to storms with fidelity, but their computational costs, the domain‐specific knowledge necessary to use them, and the wide range of potential future storm and beach conditions can hinder their use in forecasting storm erosion for short‐ and long‐term horizons. We develop an emulator, which is an efficient predictive model that behaves like a numerical model, to predict the morphologic response of the subaerial beach to storms. Specific emphasis is placed on providing antecedent beach states as an input to the emulator and predicting the post‐storm profile shape. Training data include beach profiles at multiple stages in a nourishment life cycle to assess if such a framework can be applied in locations that nourish as a coastal defense policy. Development and application of the emulator is focused on Nags Head, North Carolina, which nourishes its beaches to mitigate hazards of storm waves, flooding, and erosion. A high‐fidelity, process‐based morphodynamic model is used to train the emulator with 1250 scenarios of sea‐storms and beach profiles. The post‐storm beach state is emulated with a parameterized power‐law function fit to the eroded portion of the subaerial profile. When the emulator was tested for a sequence of real storms from 2019, the eroded beach profiles were predicted with a skill score of 0.66. This emulator is promising for future efforts to predict storm‐induced beach erosion in hazard warnings or adaptation studies.

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.

Measuring free surface elevation of shoaling waves with pressure transducers

An assessment of formulas to recover wave surface elevation from pressure measurements was carried out in the present study. The investigation focused on the formulas’ performance in the shoaling region, i.e. where the wave nonlinearity gradually increases as the wave travels towards shallower waters. Formulas based on linear wave theory alongside nonlinear reconstructions were considered. Experiments in a large-scale wave flume provided with a concrete beach profile were performed, in which regular waves were generated and surface elevation was measured with acoustic, resistive and pressure gauges. The considered formulas require the application of a cutoff frequency to the wave signal in order to avoid high frequencies amplification that progressively arise as wave shoaling occur. A simple but effective method to obtain a reference cutoff frequency is proposed in the present work; the method is based on a polynomial fitting of the unfiltered wave energy spectrum. A sensitivity analysis of each formula to the variation of this cutoff frequency was carried out. Results showed that all the investigated formulas recover wave elevation fairly well for low-nonlinearity waves, whereas overestimating wave crest height as nonlinearity increases. Wave reconstruction of the linear formulation performance was comparable to nonlinear formulations in terms of wave crest height reconstruction, although tending to amplify frequencies in the wave trough. Moreover, the performance of the formulas to correctly recover the asymmetry and flatness of the surface elevation distribution was assessed by analysing third- and fourth-order moment statistics. In this sense, nonlinear reconstruction formulas performed better in recovering the asymmetric distribution of the wave elevation, with the formula based on linear wave theory underestimating skewness and kurtosis for large nonlinearity waves.

A Copula-Based Simulation of Wave-Induced Pore Water Pressure Gradient and Local Acceleration Within Surf Zone for Natural and Laboratory Barred Beach Profiles

Wave-induced pressure gradients and local accelerations are important interconnected physical mechanisms involving several hydrodynamic and morphodynamic coastal phenomena. Therefore, to provide a reliable and realistic hydrodynamic and morphodynamic simulation, the dependencies among different parameters, such as water level, pressure gradient, local acceleration, and sediment concentration, should be considered. Herein, a copula-based simulation is presented for modeling multivariate parameters and maintaining their statistical characteristics within the surf zone. Archimedean and elliptical copula families are applied to investigate the dependency construction between the parameters in two case studies: one from a field site on the east coast of Japan, and another from a large-scale laboratory barred beach profile. The dependency between variables is evaluated using Kendall’s τ correlation coefficient. The water level, pressure gradient, and local acceleration are shown to be significantly correlated. The correlation coefficients between the variables for the natural beach are lower than the laboratory data. The marginal probabilistic distribution functions and their joint probabilities are estimated to simulate the variables using a copula approach. The performance of the simulations is evaluated via the goodness-of-fit test. The analysis shows that the laboratory data are comparable to the field measurements, implying that the laboratory simulation results can be applied universally to model multivariable joint distributions with similar hydrodynamic conditions.

A Numerical Model to Simulate Beach and Dune Evolution

Zhang, J. and Larson, M., 2022. A numerical model to simulate beach and dune evolution. Journal of Coastal Research, 38(4), 776–784. Coconut Creek (Florida), ISSN 0749-0208. A numerical model to simulate cross-shore (CS) beach and dune evolution induced by storms was developed in this study. The model development was partly based on previous CS modeling work in which modules describing the response of the beach profile in the offshore, surf, and swash zone were described in detail, but where the dune module is lacking. The dune module, adopting wave impact theory, was integrated into the previous model to complete a new numerical model. To calibrate and validate the new model, high-quality data on hydrodynamics and dune profile response from both laboratory and field data were used. The laboratory data included two experimental cases related to dune erosion from the SUPERTANK data collection project, whereas the field data consisted of two cases from Ocean City, Maryland and one case from Myrtle Beach, South Carolina. Overall, good agreement was obtained between calculations and measurements, illustrating that the model is reliable and robust in simulating beach and dune evolution. However, the poststorm beach recovery in the swash zone could not be well captured by this model. Thus, in subsequent model development, onshore transport and accretion in the nearshore will be emphasized to simulate long-term beach evolution.

Monitoring the Shoreline Dynamics of Manamoc Island, Cuyo, Palawan

Anthropogenic activities have an impact on the coastal environment, even on small islands with little economic activity. This is evident in Manamoc Island, Cuyo, Palawan. Knowledge and understanding of these impacts will enable policymakers to formulate policies arresting the problem. This study focused on establishing shoreline trends using sand boundary as a proxy and determining specific physical or natural processes and anthropogenic activities affecting coastal conditions on Manamoc Island. Key informant interview (KII), beach profiling, longshore drift direction and velocity determination, and time series analysis of shoreline were carried out. Manamoc Island coastline retreated at an average of 38–64.5m from 1989 to 2016. These were attributed to the compounding effect of natural processes, hydrometeorological events, and anthropogenic activities. The anthropogenic activities led to the destruction of natural barriers e.g. sand, rocks, coral reefs, seagrass, mangroves, and other coastal vegetation resulting in coastal erosion. With impending threats of climate change and sea-level rise, locals should consider long-term relocation. Furthermore, intensive IEC campaigns on coastal resource protection and reframing the coastal resource management plans are imperative.

Relative sea level and wave energy changes recorded in a micro-tidal barrier in southern Brazil

AbstractConstructional sedimentary history of coastal barriers can provide insights regarding meteorological and oceanographic processes, and relative sea-level changes. We investigated the Holocene evolution of a segment of the Rio Grande do Sul Coastal Plain in southernmost Brazil. Data were obtained from ground-penetrating radargrams, optically stimulated luminescence dating, altimetry measurements, Google Earth imagery, and aerial photographs. These data allowed a qualitative and quantitative analysis of the beach profiles recorded in the radargrams. From which eolian, backshore/foreshore, breaker bars, and upper and lower shoreface radar facies were identified. The beach-related radar facies are recorded in twenty-eight progradational sand units (sigmoidal bodies). These units record increments of relatively steady deposition bounded by erosional surfaces produced by anomalous, high-magnitude storm events taking place about every 250 years. The upper shoreface strata include two to three breaker bars. Several pieces of evidence (number of breaker bars, upper shoreface gradient and progradation rate) suggest an alternation between dissipative and intermediate stages of barrier morphodynamics and a decrease of wave energy from 2 ka onwards. The barrier prograded during the last 7.1 ka, and initially, barrier progradation occurred because of a normal regression during a relative sea-level rise followed by a stillstand. Later, barrier progradation took place as a forced regression driven by a relative sea-level fall.

Estimation of littoral drift for non monsoon using beach and nearshore profiles

ABSTRACT Beach profile measurements spatially and temporally or information on periodical dredging helps in assessing the littoral drift in an area. Beach profiling is one of the traditional methods to understand the beach as well as nearshore morphology in a short term. Exact quantification is always a challenging task near coasts as a part of coastal zone management activities due to the lack of enough information pertaining to sediments and its movement. In this study, the long and crossshore movements of sediments were analysed by using beach and nearshore profiles at three typical locations along South Karnataka coast in non-monsoon season. The rates of changes in areas and volumes were estimated along Gokarna, Honnavar and Malpe locations. All the locations are connected with inlets or estuaries or ports. The analysis of nearshore profiles indicated marginal changes in areas at Gokarna and Honnavar. The change is relatively more at Malpe site. The rate of volume changes of sediment over a study period increases towards south from Gokarna to Malpe and varies from 0.14 M m3 to 0.17 M m3. The potential longshore drift along the coast was also estimated whose correlation is strong with the shoreline orientations of the locations considered.

Laboratory Study on the Effect of an Artificial Sandbar on Nourished Beach Profile Evolution

Laboratory Study on the Effect of an Artificial Sandbar on Nourished Beach Profile Evolution