Beach Slope Research Articles

Indeks Kesesuaian Wisata Di Pantai Pemuteran Buleleng, Bali


 
 
 
 Marine ecotourism is one way of developing tourism in coastal areas that pays attention to ecology and maintains environmental stability. This study was conducted to determine the value of the Tourism Suitability Index (IKW) at Pemuteran Beach, Grokgak, Buleleng by considering 10 parameters such as water depth, beach type, beach width, water base material, water current velocity, beach slope, water brightness, coastal land cover, hazardous biota, and freshwater availability. The method of determining the location using the purposive sampling method is by taking an intentional and determined sample so that what you want to study can be represented by the number of stations, as many as 4 station points. The IKW analysis in this study refers to the suitability classification of coastal tourism and the tourism suitability matrix. Based on the results of the IKW analysis at Pemuteran Beach, each station, namely Station I has a value of 77%, station II is 79%, station III is 83%, and Station IV is 82%. It has the type and basic material of the beach with a black sand substrate with a mixture of coral fragments with a depth of 1.55-1.7 m; including shallow waters, the average width of the beach is quite wide, which is 11.5 m. In addition to this, Pemuteran Beach has a coastal slope of less than 10o with an average current speed of 0.27 m/s and has 100% water clarity. Coastal land cover is generally in the form of resident settlements.
 
 
 

Creating an Autonomous Hovercraft for Bathymetric Surveying in Extremely Shallow Water (

Coastal shallow water environments (<5 m) are extremely biodiverse and dynamic yet are often mapped too infrequently or at too low resolutions to capture the important processes occurring in these regions. Common forms of coastal surveying can leave gaps in data in the shallow water zone due to optical instrument capabilities and a vessel's ability to navigate in this region. One solution to these issues is an autonomous hovercraft that can fly over land and water and begin surveying at sub-meter water depths, bridging the gap between common optical and acoustic surveying methods. The craft's autonomy is tested via four autonomous flight paths, or missions, and the desired path is compared to both the observed heading and direction of motion. Although the accuracy for each track in the mission varies, most headings and directions of motion of the hovercraft are within 50 degrees of the desired direction. A single-beam echo sounder was used to map the bathymetry of the study site, showing a gently sloping beach.

A numerical model for predicting waves run-up on coastal areas

ABSTRACT In this study, numerical investigations are performed to validate a numerical model for the prediction of waves propagation and waves run-up on coastal zones. The proposed numerical model is based on the depth-averaged two-dimensional dispersive shallow water equations with source terms due to variable bottom topography and bed friction effects. We propose to solve the resulting nonlinear system using a well-balanced positivity preserving Godunov-type finite volume method on unstructured triangular grids. We used a semi-implicit scheme for the friction terms and a well-balanced formulation for the bottom topography. Moreover, we prove that the numerical scheme exactly preserves a class of nontrivial steady-state solutions. To validate the proposed numerical model against experiments, we first demonstrate its ability to preserve nontrivial steady-state solutions over a slanted surface and then we model several laboratory experiments for the prediction of waves run-up on sloping beaches. The numerical simulations are in good agreement with laboratory experiments which confirms the robustness and accuracy of the proposed numerical model in predicting waves propagation on coastal areas.

Unified analytical solution for group-induced infragravity waves based on Green's function

Short-wave group forcing is a major driving mechanism of infragravity waves. The subharmonic response to wave group forcing approaches resonance in shallow water where the group velocity is equal to the shallow-water wave-propagating speed. Currently, there is a lack of understanding of the connection between the free and bound components of group-induced infragravity waves and the consistency among existing solutions for off- and near-resonance conditions in intermediate and shallow water. Here, a unified solution of group-induced subharmonics is derived based on Green's function for the first time. The new solution is valid for any resonance intensity and is able to describe group-induced subharmonic behaviour at all water depths consistently from a new angle. The proposed solution reduces to existing solutions for intermediate depth (Longuet-Higgins &amp; Stewart, J. Fluid Mech., vol. 13, 1962, pp. 481–504; Zou, Phys. Oceanogr., vol. 41, 2011, pp. 1842–1859), shallow water and/or over a plane sloping beach (Van Leeuwen, PhD thesis, TU Delft, 1992; Schäffer, J. Fluid Mech., vol. 247, 1993, pp. 551–588; Janssen et al., J. Geophys. Res., vol. 108, 2003, p. 3252; Contardo et al., J. Phys. Oceanogr., vol. 51, 2021, pp. 1465–1487; Liao et al., J. Phys. Oceanogr., vol. 51, 2021, pp. 2749–2765). Unlike previous solutions, the Green's function-based solution describes all subharmonics as free subharmonics continuously radiated away from each point source in the group-induced forcing field determined by wave radiation stress gradients. The superposition of all these free subharmonics yields so-called bound subharmonics by previous studies due to group-modulated emission of each free subharmonic through the source field bound to the wave group. Therefore, this solution provides theoretical evidence that the group-induced subharmonic at any observation point is dependent on the surrounding radiation stress field and topography. Under full-resonance conditions in shallow water, downwave-propagating subharmonics excited at all source locations interfere with each other constructively; therefore, their superposed amplitude is proportional to the travel distance of wave groups. Combined with the conventional moving-breakpoint forcing model, the predicted amplitude of the subharmonic in the surf zone by the present solution is in good agreement with laboratory observations.

Multiple Seepage‐Faces in Tidal Flat With Very Gentle Slopes

AbstractLarge‐scale seepage‐faces occur on small‐slope tidal flats. All previous studies assume that the seepage‐face has only one single exit point. Here we show via numerical simulations of tidally‐influenced groundwater flow that, in a two‐dimensional vertical, homogeneous transect of a tidal flat with gentle beach slope of 1‰, multiple seepage‐faces may occur with at most four unsaturated beach surface segments which separate four seepage‐faces. Salinity‐variation induced density‐dependent flow leads to this complex phenomenon. While the seepage‐faces are the groundwater discharging zones on the beach surface, the unsaturated zones are the recharging zones. The whole aquifer beneath the tidal flat is almost occupied by seawater and forms a wall blocking the horizontal seaward discharge of inland fresh groundwater so that inland freshwater discharges mainly occur near the high tide mark. This is in great contrast with the traditional results that inland freshwater discharge occurs mainly near low tide mark.

Inverse problem for the nonlinear long wave runup on a plane sloping beach

We put forward a simple but effective explicit method of recovering initial data for the nonlinear shallow water system from the reading at the shoreline. We then apply our method to the tsunami waves inverse problem.

Site Suitability Analysis for Sea Turtle Nesting Area by using AHP and GIS

Sea turtles are among the endangered marine life not only in Malaysia but also in the world. There are various criteria required in finding a suitable turtle nest site, it may be necessary to suit the needs of the environment in the study area, and it was found that there are four (4) most important criteria in studying turtle nesting suitability site namely (1) sand temperature, (2) vegetation, (3) beach slope, and (4) sand particle size. The use of GIS with the help of AHP can get a better result in finding the site suitability for sea turtle nesting by using weighted overlay analysis. The highest weight value is sand particle size with 0.616, followed by beach slope with 0.220, sand temperature with 0.114, and vegetation with 0.049 was derived from the use of AHP techniques. As a result, the suitability index in the study area was measured and analyzed with the sea turtles’ activities. As a result, the suitability index in the study area was measured and analyzed with the sea turtles’ activities. It was found that there is a low correlation between the site suitability index and the sea turtles’ activities which matches the expert’s opinion that though the site is deemed suitable for sea turtles nesting, they may not be crawled up and nest due to other external factors. The sites with the highest index were verified to be the most suitable by the experts as it is true that sea turtles were ascending to the sites for nesting. In conclusion, integrating GIS with the help of AHP can be an important technique to find a suitable site for the sea turtle nesting area.

Spawning habitat suitability maps for the conservation of the tri‐spine horseshoe crab Tachypleus tridentatus in Tsuyazaki Cove, Fukuoka, Japan

Abstract The suitable spawning habitat of Tachypleus tridentatus was estimated and mapped for the first time using scientific modelling in Tsuyazaki, Fukuoka, Japan. A total of 43 nests were found at five sites from 2018 to 2019. Of these 43 nests, the location information of nine nests at one of the sites was used as ‘Training data’ for constructing the models. A series of procedures was employed to determine the relationship between the biological data and their physical parameters to estimate the suitable spawning habitat. First, the contribution rates of the physical parameters (beach elevation, slope and sediment) to nest locations were evaluated. Second, physical parameters that showed significant contribution rates were chosen to estimate suitable spawning habitats. It was found that the beach elevation was the most significant parameter for estimating suitable spawning habitats. Mean high water neap to mean higher high water was estimated as suitable spawning habitat, and 74% of the nests were fitted in an area assessed as suitable. The result was consistent with previous studies. The area of suitable spawning habitat was estimated to be only 476 m2 out of 1943 m2, comprising 24% of the sandy beach in the study site. Therefore, it was concluded that the conservation and restoration of spawning grounds is a high‐priority and urgent issue at the site. It is proposed that scientific modelling of nest/egg occurrence and beach elevation can effectively determine suitable spawning habitats. Thus, it is possible to quickly establish the habitat most suitable for spawning in coastal environments and help plan conservation strategies for this globally endangered species.

Coastal Dynamics Analysis Based on Orbital Remote Sensing Big Data and Multivariate Statistical Models

As the interface between land and water, coastlines are highly dynamic and intricately tied to the sediment budget. These regions have a high functional diversity and require enlightened management to preserve their value for the future. In this study we assess changes to the São Paulo State (SE Brazil) coastline over the last 36 years. The study innovatively employs big data remote sensing techniques and multivariate statistical models to evaluate and generate erosion/accretion rates (1985–2021) relative to beach orientation and slope. Shoreline change rates have been obtained for sandy beaches at 485 one-kilometer-spaced transects. Our findings capture the complexity and heterogeneity of the analyzed coastline, at a regional and local scale. No association was found between shoreline changes and beach face orientation. Nonetheless, a dependency relationship was found between dissipative beaches with moderate to high accretion. Beaches facing south, with relative stability, were prone to sediment accumulation. Locations with slow accretion, like sandy spits and tombolo-protected beaches, were associated with dissipative beaches with moderate to high accretion. The southeast-oriented beaches are more prone to erosion due to storm waves from the south. Results provide a broad, fast, and relatively low-cost methodology that can be used in any sandy beach context, bringing essential information for coastal management and decision-making related to the use and occupation of the coastal zones.

A predictive equation for wave setup using genetic programming

Abstract. We applied machine learning to improve the accuracy of present predictors of wave setup. Namely, we used an evolutionary-based genetic programming model and a previously published dataset, which includes various beach and wave conditions. Here, we present two new wave setup predictors: a simple predictor, which is a function of wave height, wavelength, and foreshore beach slope, and a fitter, but more complex predictor, which is also a function of sediment diameter. The results show that the new predictors outperform existing formulas. We conclude that machine learning models are capable of improving predictive capability (when compared to existing predictors) and also of providing a physically sound description of wave setup.

Watertable fluctuations in coastal unconfined aquifers with a sloping sea boundary: Vertical flow and dynamic effective porosity effects

Interactions between the tide and sloping sea boundary make watertable fluctuations in coastal unconfined aquifers complicated. Based on a perturbation method, we derived a new analytical solution to predict watertable fluctuations for coastal unconfined aquifers with a sloping sea boundary. Following validation with a numerical model, the analytical solution was used to explore the effects of the vertical flow (in the saturated zone) and dynamic effective porosity on watertable fluctuations. Results show that the new analytical solution accurately predicts watertable fluctuations for coastal unconfined aquifers with a sloping sea boundary. Compared with sand coastal unconfined aquifers, both vertical flow and dynamic effective porosity effects on watertable fluctuations are more pronounced for loam coastal unconfined aquifers. Vertical flow has a minor influence on the fluctuation amplitude while it significantly decreases the phase lag of the watertable fluctuation at a given location. In contrast to vertical flow, accounting for the dynamic effective porosity not only decreases the phase lag, but also significantly amplifies the fluctuation amplitude for a given location, which enables watertable wave propagation further inland. Increasing the beach slope weakens the effects of the vertical flow and dynamic effective porosity on watertable fluctuations. Furthermore, including either the vertical flow or dynamic effective porosity effects leads to a lower watertable overheight. These results highlight the importance of vertical flow and dynamic effective porosity effects in models of watertable fluctuations.

The solitary wave run-up on sloped beaches protected by submerged rigid breakwaters

The reduction of wave run-up induced by solitary waves at sloping beaches, by means of submerged barriers has been investigated. To this purpose, 198 laboratory tests were undertaken in the wave channel of the University of Calabria, by adopting three beach slopes, three water depths and square and rectangular rigid type-barriers. To make comparisons on the performance of the barriers in reducing the run-up, 99 tests were carried out considering the same experimental conditions, without the barriers. Two approaches were used to deduce the resulting solitary wave run-up in the presence of the barriers starting from the knowledge of wave parameters without them. The first approach uses the wave amplitude, whereas the second, more physically based, uses the wave energy, depending on the horizontal velocity and the wave pressure. Based on the calculation of the transmission coefficients using the dimensional analysis, the transmitted wave amplitude and energy after the barriers were deduced. Using these quantities, the recent semi-empirical formulas deduced by Casella et al. (2022) in the absence of the barriers were extended to determine the solitary wave run-up in their presence.

Influence of living shoreline elements on wave run up elevations

Nature-based coastal protection, also known as engineering with nature or living shorelines, is becoming increasingly popular due to its dual benefits of reducing coastal flooding and providing ecological and recreational opportunities. In many coastal areas experiencing chronic erosion, changes in sediment supply, composition, and grain size are significant contributing factors to shoreline recession. One living shoreline strategy to consider includes the application of cobbles over more traditional sand nourishments. On sandy beaches that experience high-energy wave conditions, the introduction (or reintroduction) of cobbles can mitigate backshore erosion. Cobble-backed beaches have been found to mitigate the effect of coastal erosion and flooding in laboratory settings and field observations, and they have recently been piloted in locations such as Cape Lookout State Park in Tillamook County, Oregon, and Surfers Point in the City of Ventura, California. However, there are no formal engineering guidelines stipulating the calculation of wave run-up on cobble-backed beaches. This study applies three different wave run-up equations on a living shoreline design (i.e. mixed sand and cobble berm-backed beach) in Malibu, California, and compares the predicted run-up levels with existing condition flood levels for typical and eroded conditions. The different wave run-up equations were designed for cobbles only, revetments, and composite beaches, respectively, where the composite beach equation was most applicable to project design. For typical beach conditions (higher levels of sediment accretion resulting in shallower beach face and berm slopes), all three equations showed a reduction in wave run-up values. When applied to worst-case conditions (i.e. scoured by a creek channel and steeper fronting beach slopes), the equation most applicable to the design showed the highest reduction of total water levels. A sensitivity analysis found that the cobble-backed beach equation predicted the most consistent values of run-up (run-up values changed the least), even when input parameters (slope and water depth) changed. This study shows that cobblebacked beaches hold promise to mitigate coastal flooding in appropriate areas, in addition to being a natural solution for areas experiencing erosion. This study also points to the need for more studies and field observations to validate the run-up levels determined here.

The physical processes of sandy beach evolution under storm and non-storm wave conditions simulated in wave flume

Large waves and high water levels generated by coastal storms are predominant drivers for coastal beach erosion. This experimental study is undertaken to investigate the physical processes of beach profile evolution under storm waves by simulating step varying storm waves and variable water levels in a wave flume of 30 m long, 0.6 m wide and 1 m high and mild beach slope tanθ=1/10. The storm waves were simulated by following a conceptual storm hydrograph of three stages: at the first stage of 60 min both wave height and water level were gradually increased to peak storm wave height and water level, at the second stage of 60 min both maximum wave height and water level were kept for constant, and at the last stage of 60 min storm wave heights were gradually decreased to non-storm waves and water levels. Non-intrusive high-resolution cameras were used to record time-series of free surface water elevation, wave breaking point position, sandbar migration and location, and beach elevation profile in a spatial resolution of 1.4 mm and a temporal resolution of 0.1 s. In analyzing the collected experimental data, the physical processes of beach evolution under both non-storm and storm waves were found significantly different: under non-storm waves, the movement of sandbar always was found to be in the seaward direction, and the beach profile was eroded and accreted before and after the sandbar, respectively, but under storm waves, the sandbar location was found to migrate in either the landward or seaward direction, the beach profile was slowly accreted before the sandbar and eroded after the sandbar when the storm waves were gradually decreased to the non-storm waves. The surf zone is the main change area in beach morphology modification, and the sandbar is the important indicator for distinguishing the cross-shore sediment exchange. Under both non-storm and storm waves, large waves, high water levels, and especially great gradient of wave energy flux due to changes in wave height, period and water depth are the main factors controlling the formation and migration of sandbar, and resulting in beach erosion and accretion before and after the wave breaking point, respectively.

The Concept of Integrated Coastal Management for Eco-Tourism Development at Dalegan Beach, Gresik Regency, East Java, Indonesia

Indonesia has enormous potential in the maritime sector, specifically in the tourism sector. Tourism in Indonesia is developing in several regions. There is one of the tourism destinations in Gresik Regency, that is Dalegan Beach. Dalegan Beach is located in Dalegan Village, Panceng District which has an area of 6.39 km2. Dalegan Beach has an area of about 2.3 ha and a beach length of about 180 meters. Dalegan Beach has a potential eco-tourism because of sloping beach topography, calm waves and white sand. However, to develop the Dalegan Beach as an eco-tourism have several obstacles. There are lack of infrastructure to support tourist attractions, unclear collaboration between the village community and the local government, and poor management so that the development of eco-tourism is not optimal. This study aims to improve the management of Dalegan Beach as eco-tourism, which involved all stakeholders include local governments, communities, regional consultative bodies and universities. The Analythic Hierarchy Process (AHP) method is applied on this study in order obtaining an integrated and sustainable beach management formula based on priority scale. There are five factors used for the criteria in this analysis process, those are environmental, economic, social, infrastructure, and legal. Furthermore, the Expert Choice software are used to process inputs gained from the stake holders. The result of analysis indicates the order of alternative priority management that must be carried out namely human resource empowerment of 0.336 or (33.6%), then the development of tourist destinations with a value of 0.256 or (25.6%), further development of tourism marketing of 0.238 or (23.8%) and finally industrial development of 0.170 or (17.0%).

Wave runup and inundation dynamics on a perched beach

Sandy beaches perched over rocky shore platforms are common globally, yet their mixed sand and rocky morphology present challenges for quantifying and predicting wave runup and inundation. For typical linear beach profiles, simple relationships can be made between vertical runup and horizontal inundation based on beach slope. However, as topographic irregularities increase, substantial deviations from these relationships can occur. Shore platforms often experience a range of beach states, from full sand coverage (accreted) to complete shore platform erosion (exposed). As a result, existing methods for quantifying runup and inundation on purely sandy beaches are generally not directly applicable to these coastlines. To advance our understanding of runup and inundation on perched beaches, the aim of this work is three-fold: (1) to provide a method for quantifying beach slope and runup across a range of perched beach profiles, (2) to assess the relationship between vertical runup and horizontal inundation observations, and (3) to understand how different hydrodynamic mechanisms (i.e., setup, swash) contribute to runup during different beach states. To achieve this, we conducted an 8-month field study along a perched beach in southwestern Australia that experiences large seasonal variations in beach state and wave climate. A method was developed to measure runup and beach slope when only the topography shoreward of the shore platform edge was known. Using this method, an approximately linear relationship between inundation and runup was identified by incorporating beach slope. Our observations suggest that the components that dominate runup on perched beaches were primarily dependent on beach state (i.e., accreted versus exposed). Runup was dominated by swash in the infragravity band when in an accreted beach state, and setup when in an exposed beach state. These results aid our understanding of coastal processes on perched beaches, while providing new methods applicable to a range of perched beach profiles.

Numerical Investigation of Reducing Wave Propagation Hazard Utilizing an Appropriate Vegetation Area

In this study, a numerical model was employed to determine the optimal location for vegetation as an environmentally friendly method of attenuating tsunami waves. The governing equations are shallow water equations solved using shock-capturing schemes with second-order accuracy model. This simulation was validated using experimental data and another numerical model for simulating the propagation of tsunami waves on a vegetated horizontal bed and vegetated sloping beach. The parameters of wave damping rate, maximum velocity, and height for the plant area at various locations and vegetation zone lengths were investigated using numerical models. By increasing the length of the plant zone, the height and velocity of the tsunami wave were reduced, and the wave damping was increased. The examination of various locations and lengths of the plant area demonstrated that the plant area’s distance from the shoreline is a significant factor in coastal protection. The results exhibit that the location of the forest area has a great impact on the control of destructive factors along the beach. As a result, this study provides some information for designing a tsunami-resistant forest area.

The effect of groins characteristic on sandy beach stability

Groins are one of the most important facilities used to protect coastal regions. In this research, groins made from a concrete cube were tested experimentally. This research investigates the impact of groin length (Lg) of 105, 135, and 165 cm and groin angle with the normal axis of the shoreline (θ) of 0°, 10°, 20°, and 30° under different dimensionless wave numbers (khg), from 0.34 to 1.26, with the beach slope of 8:1. The units used to indicate erosion and deposition are dimensionless erosion depth (Smax/h), dimensionless deposition height (Dmax/h), and dimensionless erosion hole length (lsmax/h). The sandy bed changes and wave reflection from the groin were monitored. The results showed that the angle of 30° had more impact on beach stability than that of 0°, and more sediments were eroded by short groins than by long ones. The reflection of waves from groins was also studied as a function of the reflection coefficient (kr). As concluded, short groins reflect higher waves than long ones.

Influence of Environmental Conditions on Mytilus trossulus Size Frequency Distributions in Two Glacially Influenced Estuaries

The Pacific blue mussel (Mytilus trossulus) is a foundation species in high-latitude intertidal and estuarine systems that creates complex habitats, provides sediment stability, is food for top predators, and links the water column and the benthos. M. trossulus also makes an ideal model species to assess biological responses to environmental variability; specifically, its size frequency distributions can be influenced by the environment in which it lives. Mussels that inhabit estuaries in high latitudes receive freshwater runoff from snow and glacial-fed rivers or can be under oceanic influence. These hydrographic conditions work together with local static environmental characteristics, such as substrate type, fetch, beach slope, distance to freshwater, and glacial discharge to influence mussel demographics. In 2019 and 2020, mussels were collected from two Gulf of Alaska ecoregions to determine whether mussel size frequencies change over spatial (local and ecoregional) and hydrographic scales and whether any static environmental characteristics correlate with this variability. This study demonstrated that mussel size frequencies were most comparable at sites with similar hydrographic conditions, according to the ecoregion and year they were collected. Hydrographic conditions explained approximately 43% of the variation in mussel size frequencies for both years, for the combined ecoregions. Mussel recruits (0–2 mm) were more abundant at sites with higher fetch, while large mussels (> 20 mm) were more abundant at more protected sites. Fetch and freshwater influence explained most of the variation in mussel size frequencies for both years and across both ecoregions, while substrate and slope were also important in 2019 and glacial influence in 2020. This study suggests that hydrographic and static environmental conditions may play an important role in structuring mussel sizes. Although differences in mussel size frequencies were found depending on environmental conditions, mussel sizes showed little difference across differing types of freshwater influence, and so they may be resilient to changes associated with melting glaciers.

Analytical modeling of contaminant transport along sloping coastal beaches in presence of tidal waves and exponential rainfall infiltration

Coastal beaches are the most important part of the marine environment and are highly influenced by the interactions taking place between groundwater and surface water of any form. Generally, the purity index of the groundwater is based on the concentration of Total Dissolved Solids (TDS) in it. Analytical solutions are the best tools for groundwater flow and transport modeling. However, contaminant transport along the sloping coastal beaches with complex boundaries cannot be addressed with available analytical solutions. In the present study, new analytical models are developed for groundwater flow and contaminant transport for sloping coastal beaches with continuity and tidal boundary conditions. To assess the performance of the new analytical solution and to validate the range of aquifer parameters, numerical simulation is performed using Du-Fort Frankel (DFF) Scheme. Numerical experimentation is carried out using the Tchebycheff and L2 norms. It is observed that the new analytical solution for the contaminant transport gives acceptable results over the wide range of the aquifer parameters. To show the effectiveness of the developed models, two case studies from Indian coastal aquifers namely, Kalpakkam, Tamil Nadu, and Bhavnagar, Gujarat are considered. The profiles of the contaminant concentration are obtained to study the TDS behavior along these complex coastal beaches in the spatiotemporal directions. The results are compared with numerical model results and found to be satisfactory. The combined effect of the initial rainfall and rainfall decay constants showed a significant impact on the concentration of TDS. TDS concentrations are observed to be varying highly with the variation in the tidal constituents and bed slope.