Tidal monitoring on sandy beaches using perpendicular time-lapse photography

<p><span>Long term time-lapse photography has proven to be a key tool in monitoring changes in coastal environments, particularly in terms of morphology. The present study adapts and simplifies the approach of some precedents, such as the Argus and CoastSnap systems, to remotely monitor tidal inundation on a sandy beach at Magilligan on the north coast of Northern Ireland. Such a system could prove essential in the study of the effect of waves and tides on groundwater flow and saline intrusion in coastal aquifers, its consequences for sensitive subsurface infrastructure (such as water supply wells), and in the reconciliation of continuous data from same. Photographic data in this study have been gathered using a remote, solar powered time-lapse camera over a six-month period, capturing full neap and spring tidal cycles. Images are captured at hourly intervals and automatically uploaded to the cloud for remote access. The camera is located just 25 metres from the high water mark, overlooking the beach and perpendicular to the sea. This setup contrasts with previous studies where there is a need to find an elevated location at greater distance from the area of investigation. The extent to which a tide inundates up a sandy beach is governed primarily by astronomical effects, which are considered in this study, but also beach slope and atmospheric conditions. It is known that the beach at Magilligan has both a shallow grade (0.02 m) and a high tidal variation (> 150 m between spring and neap tides). Profiles of beach slope are gathered using a differential GPS, while a solar weather station on site, which also uploads data to the cloud, is used to gather atmospheric data. For tidal reference, a traditional tide gauge measuring tide levels at a pier 15 km east of the site is used. Captured images are post-processed using image analysis techniques based around characterising the tidal front against the visual contrast between pixels of sand and pixels of seawater using a routine in MATLAB</span><span><sup>®</sup></span><span>. From this analysis, a numerical value for tidal inundation is extracted. Analysis of these data indicates that the tide times (timing of high and low tides) correspond well with those measured at the nearby tide gauge, however important differences exist in terms of magnitude. In comparing these differences with atmospheric data from the site, it is possible to align larger and smaller inundation events with shifts in wind direction and speed. The calibration process involved in digitising the captured images is time-consuming, however, it may be possible to predict tidal inundation from a site using only a remote weather station — knowing how a change in wind speed or direction will affect inundation on the beach. It has already been shown that such instrumentation can be used to detect changes in beach morphology (as a key element in tidal inundation), this research therefore represents an important development in the low-cost remote monitoring of tidal inundation, particularly in locations where regular ground surveying is challenging. </span></p>

Simulation of Bay-Shaped Shorelines after the Construction of Large-Scale Structures by Using a Parabolic Bay Shape Equation

Among the various causes of coastal erosion, the installation of offshore breakwaters is considered the main cause that influences the most serious changes in shorelines. However, without a proper means for predicting such terrain changes, countries and regions continue to suffer from the aftermath of development projects on coastal land. It has been confirmed that the parabolic bay shape equation (PBSE) can accurately predict shoreline changes under the wave climate diffracted as a result of such development projects. This study developed a shoreline change model that has enhanced the previous shoreline change models by applying PBSE to shoreline changes into bay-shaped features. As an analytical comparison with the second term of the GENESIS model, which is an existing and well-known shoreline change model, a similar beach erosion width was obtained for a small beach slope. However, as the beach slope became larger, the result became smaller than that of the GENESIS model. The validity of the model was verified by applying it to satellite images that demonstrated the occurrence of shoreline changes caused by breakwaters for seaports on the eastern coast of Korea; Wonpyeong beach, Yeongrang beach, and Wolcheon beach. As a result, each studied site converged on the static equilibrium planform within several years. Simultaneously, the model enabled the coastal management of the arrangement of seaports to evaluate how the construction of structures causes serious shoreline changes by creating changes to wavefields.

Beach slope distribution mapping using UAV in the Cirebon coastal area

The beach slope is usually estimated using the conventional ground survey, causing the availability of this parameter data to be limited in some areas. Meanwhile, this parameter is considered crucial in the study of shoreline changes and coastal area protection as well as other coastal morphodynamic research. The aim of this study is to demonstrate an efficient technique to calculate the beach slope as well as its distribution in an area. In the daily intertidal period, the beach profile is assumed to be a static planar beach state which does not change due to the insignificant effect of erosion and accretion process. First, the shoreline data set was delineated from the tidal-varied orthomosaic using the UAV. The beach slope is then calculated by comparing the difference in tide level with the difference in the horizontal distance of shoreline points along a cross-shore transect at different times. The utilization of UAV allows mapping the shoreline in an area in several different tidal conditions, allowing the distribution of the beach slope also be mapped. This technique was then applied in the Cirebon Coastal Area and found an average beach slope of 0.105 with 0.100 being the slope class with the highest number of distributions. It was also found that due to the presence of mangroves and coastal structures, no slope conditions dominated this area. The result of beach slope calculation using this technique shows suitability with other studies and reveals UAVs’ potential in mapping the beach slope distribution more efficiently.

BREAKING AND WASH UP OF SOLITARY WAVES ON A COMPOSITE BEACH

Hazardous events, such as landslides, rock slides, rock falls or avalanches often generate extreme, impulsive waves when entering water bodies (Fuchs & Hager, 2015). These waves are approximated by solitary waves and researchers investigate their damage potential when inundating built environment. Deepening the understanding of solitary waves running up a uniform beach slope and propagating over a subsequent horizontal plane can help to reduce and mitigate damage and the number of casualties caused by such a hazardous event. So far, few authors addressed this specific setting near-shore (Fuchs & Hager, 2015; Zelt & Raichlen, 1991). In this study, large scale solitary waves propagate about 200 m in in the Large-Wave Flume (GWK, 307 m 5 m 7 m) at the Coastal Research Center in Hannover, Germany then they run up a beach slope and subsequently break, generating a bore which advances onto a subsequent, initially dry, horizontal surface. Unlike previous studies, the generated solitary waves broke close to the edge between the beach slope and the horizontal plane section. The overall aim of this study is to investigate the characteristics of the broken waves' dynamics. In addition, their surge profile and front celerity are compared to those of the non-breaking solitary waves. Subsequently, the differences between the velocity regimes along the bore propagation path are presented and linked to the fundamental physical processes behind.

SEDIMENTOLOGY OF BEACHES IN NORTHERN PALM BEACH COUNTY, FLORIDA, USA

Beach nourishment is a common strategy for erosion mitigation that also increases coastal resilience to storm impacts, provides habitat, and supports the economy. Regulations often require that placed sediment closely match the native grain size distribution and composition, however characteristics can vary based on the borrow site. Certain sediment properties will also influence beach slope and other critical beach functions. This study evaluates the 3-dimensional sediment properties and beach morphology of nourished and non-nourished barrier island beaches in northern Palm Beach County, Florida, USA. Surveyed beach profiles were compared with predicted slope based on median grain size. The inlet-adjacent beach managed with annual placement of beneficial use of dredged materials consisted of poorly sorted coarse sand and the steepest measured slope. Sediment was progressively finer and better sorted downdrift with decreasing foreshore slopes. Although sediment near the shoreline is typically the coarsest, clasts were finer than the mid-beach location suggesting that the sampling period coincided with beach recovery and onshore sediment transport of finer material. Sediment at the surface differed from sediment at depth, likely due to the frequent introduction of sediment from various borrow areas compared to the dominance of weathered coquina at depth. The non-carbonate, siliciclastic fraction was primary quartz with few other minerals. The estimated beach slope at the location with the coarsest sediment matched the measured slope. A lower beach slope was predicted for the other locations with finer grain sizes at the shoreline that was attributed to slightly steeper slopes associated with beach accretion. Therefore, complicated spatio-temporal morphodynamics of beaches should be considered when using median grain size from only one sampling event.

KEMIRINGAN LERENG DAN GRANULOMETRI SEDIMEN GISIK TANJUNG MERAH, BITUNG SULAWESI UTARA

ABSTRACTBeach slope and sediment granulometry is one of the importat aspect in coastal management. Beach offers a variety of functions and potential to be utilized. In the interests of phisical use in the beach, coastal structure in the form of groynes has been built. Actually, the groin has been used as a dock. This research was conducted with the aim of revealing the slope and granulometry sediment in Tanjung Merah beach. The results obtained, the beach slope is considered sloping and very sloping, the composition of the sediment consists mainly of medium sand, fine sand and very fine sand. Sediment distribution analysis obtained results, the main grain size was mainly in the form of medium sand, sorting was mainly classified as poor, skewness was mostly asymmetrie strong to large size, most curtosis was mesokurtic. The results of the study indicate the occurrence of the process of erosion and deposition ia certain spaces on the beach studied. Keywords: Tanjung Merah, beach slope, sediment granulometry Kemiringan lereng dan granulometri sedimen gisik merupakan salah satu aspek penting dalam pengelolaan pantai. Gisik menawarkan beragam fungsi dan potensi untuk dimanfaatkan. Dalam kepentingan pemanfaatan lahan gisik, berbagai modifikasi dilakukan oleh manusia. Pada gisik di Tanjung Merah, telah dibangun struktur pantai berupa groin. Secara aktual, groin tersebut telah difunsikan sebagai dermaga. Penelitian ini dilakukan dengan tujuan mengungkapkan kemiringan dan granulometri sedimen di gisik Tanjung Merah. Hasil penelitian yang diperoleh, lereng gisik terkriteria miring dan sangat miring, komposisi sedimen terutama terdiri dari pasir sedang, pasir halus, dan pasir sangat halus. Analisis distribusi memperoleh hasil, rataan empirik terutama berupa pasir sedang, penyortiran terutama terklasifikasi buruk, kemencengan terbanyak berupa asimetris kuat ke ukuran besar, peruncingan terbanyak berupa mesokurtik. Hasil studi mengindikasikan terjadi proses erosi dan deposisi pada ruang-ruang tertentu di gisik yang ditelaah.Kata kunci : Tanjung Merah, kemiringan lereng, granulometri sedimen

KEMIRINGAN LERENG DAN GRANULOMETRI SEDIMEN GISIK TANJUNG MERAH, BITUNG SULAWESI UTARA

Beach slope and sediment granulometry is one of the importat aspect in coastal management. Beach offers a variety of functions and potential to be utilized. In the interests of phisical use in the beach, coastal structure in the form of groynes has been built. Actually, the groin has been used as a dock. This research was conducted with the aim of revealing the slope and granulometry sediment in Tanjung Merah beach. The results obtained, the beach slope is considered sloping and very sloping, the composition of the sediment consists mainly of medium sand, fine sand and very fine sand. Sediment distribution analysis obtained results, the main grain size was mainly in the form of medium sand, sorting was mainly classified as poor, skewness was mostly asymmetrie strong to large size, most curtosis was mesokurtic. The results of the study indicate the occurrence of the process of erosion and deposition ia certain spaces on the beach studied.Keywords: Tanjung Merah, beach slope, sediment granulometryKemiringan lereng dan granulometri sedimen gisik merupakan salah satu aspek penting dalam pengelolaan pantai. Gisik menawarkan beragam fungsi dan potensi untuk dimanfaatkan. Dalam kepentingan pemanfaatan lahan gisik, berbagai modifikasi dilakukan oleh manusia. Pada gisik di Tanjung Merah, telah dibangun struktur pantai berupa groin. Secara aktual, groin tersebut telah difunsikan sebagai dermaga. Penelitian ini dilakukan dengan tujuan mengungkapkan kemiringan dan granulometri sedimen di gisik Tanjung Merah. Hasil penelitian yang diperoleh, lereng gisik terkriteria miring dan sangat miring, komposisi sedimen terutama terdiri dari pasir sedang, pasir halus, dan pasir sangat halus. Analisis distribusi memperoleh hasil, rataan empirik terutama berupa pasir sedang, penyortiran terutama terklasifikasi buruk, kemencengan terbanyak berupa asimetris kuat ke ukuran besar, peruncingan terbanyak berupa mesokurtik. Hasil studi mengindikasikan terjadi proses erosi dan deposisi pada ruang-ruang tertentu di gisik yang ditelaah.Kata kunci : Tanjung Merah, kemiringan lereng, granulometri sedimen