Grain-Size Distribution of Surface Sediments in the Chanthaburi Coast, Thailand and Implications for the Sedimentary Dynamic Environment

This paper analyzes the grain-size distribution of surface sediments of the Chanthaburi coast of Thailand to investigate the sedimentary environment and its evolution to better use and protect the coast. The Flemming triangle method, the grade-standard deviation method, and the Gao–Collins grain-size trend analysis method (GSTA model) were used to study the dynamic sedimentary environment of the area and provide preliminary identification of source materials. There are seven types of surface sediments on this coast, with grain sizes (φ) generally consisting of sand and silt. Sorting is generally poor, and becomes gradually poorer with distance offshore. Skewness is generally positive. The study area is mainly composed of sand and silt, indicating that the hydrodynamics are strong. The results of grade-standard deviation analysis indicate that sediment grain size b (3.25–4.5φ) is a sensitive indicator of environmental change. This sediment type exhibits a relatively complex transport trend, mainly characterized by northwestward and northeastward transport from sea to land. Sediments at the mouth of the Chanthaburi Estuary and the Welu River fluctuate under the influence of tidal currents. Based on the results of grade-standard deviation analysis and grain-size trend analysis, the study area was divided into three provinces, representing different sedimentary environments and material sources. Compared with tidal-controlled estuaries in the temperate regions of eastern China, the two tropical estuaries examined in this study exhibited smaller suspended sediment loads, runoff amounts, and tidal ranges. However, hydrodynamic conditions were generally stronger. The main reasons for the similarities and differences in the transport trends of sediments in these estuaries were differences in hydrodynamic conditions and the specifics of regional topography.

DETERMINING TEXTURAL AND GEOCHEMICAL ELEMENT CHARACTERISTICS OF SEAFLOOR SEDIMENT USING MULTIVARIATE ANALYSIS ALONG THE SIMEULUE SUB-BASIN, INDONESIA

The Simeulue sub-basin is situated off north-western Sumatra between the outer arc and the mainlands. The sediment and geochemical element characteristics of basins are the important sedimentology variables to recognize the process of sediment deposition. However, the characteristics of the sediment and the geochemical elements in the Simeulue subbasin have not been well explained. This study aims to investigate the textural and geochemical elements characteristics of marine sediments and the distribution of these two variables to determine the sedimentary facies in the Simeulue sub-basin. Samples were taken from various depths in the sub-basin and collected during the 2017 Expedition of “Widya Nusantara” by using the “Baruna Jaya VIII” Research Vessel. The grain size trend analysis showed that the middle part of the basin was dominated by mud, while the edge of the basin near the island (mainland) was mostly dominated by coarser sediments. A geochemical element analysis was performed on each sample to observe the origin of the sediments. The results of these two analyses were subjected to multivariate statistics. This approach was selected because it is appropriate for determining the sedimentary facies and the depositional environments. Based on the multivariate analysis, the sedimentary facies in the Simeulue sub-basin was divided into five facies with similar sediment characteristics and depositional environments. These facies were deposited in the environment with low to medium energy.

Coastal Sediment Transport along Kalpakkam using Sediment Trend Exploaration and Numerical Modelling

The impact of coastal sediment transport in the nearshore region is significant and the need for improved sediment quantification techniques appears to be universally accepted. The coastal sediment transport models presently in use were derived empirically from very sparse measurements of waves and currents and from laboratory experiments. The shoreline of Kadalur fishing villages near Kalpakkam has been experiencing erosion due to occurrence of cyclones every monsoon. Palar River with its confluence in the Bay of Bengal at the northern tip of the Kadalur villages has its mouth closed due to negligible river flow. The purpose of this study is to assess sediment dynamics in the Kalpakkam coast using two independent approaches; namely Sediment Trend Analysis (STA) and two dimensional numerical modelling. The latter can track the movement of individual particles. Numerical modelling approach is based on Delft3D model which allows the coupling of flow and wave modules. STA and numerical modelling results can provide sediment transport direction. The combination of both approaches provides a means of verification of sedimentation processes. The basic assumption in STA is that sediment transport can be responsible for the differences in sediment grain size distributions. For Grain Size Trend Analysis, grab samples were collected throughout the nearshore area. Grain Size Trend Analysis was then carried out and subsequent results were plotted to obtain the sediment transport pattern for the region. The results obtained are compared with the numerical model results and also used for validation of sediment transport evaluated using the numerical model.

Characteristics of Grain Size Distribution on Beaches Sediment of Sumba Island, Nusa Tenggara Timur Based on Grainsize and Geochemical Data

Study of beaches sediment characteristics were conducted on three beaches on Sumba Island, East Nusa Tenggara.The research is a part of Widya Nusantara Expedition which conducted by using Research Vessel of Baruna Jaya VIII. The aim of this study is to determine the characteristics of coastal deposits through the observation of grain size by using the grain size trend analysis approach (Grain Size Trend Analysis, commonly abbreviated as GSTA) and geochemical analysis. A total of 36 samples were taken on each coast representing high tide, transition and low tide along the coast. A grain size analysis was performed using a Malvern Mastersizer 2000 that was processed with Gradistat 4.0 software. Geochemical analysis was carried out using X-ray fluorescence spectrometry (XRF). The distribution of beach sediments is dominated by moderate sand - coarse sand and differences on content of geochemical elements (Ca, Sr, Fe, K, and Ti). The coastal conditions that are connected to the Indian Ocean (B1) have different characteristics from the beach that connected to the Sumba strait (B5 and B7). GSTA analysis showed sediment of Laboya Beach finer than sediment on Waikelo and Melolo Beach. Geochemical elements on Laboya Beach indicates different values than others. It indicates there are differences in the provenance and composition of sediment on the all three beaches. The supply of coastal deposits on these three beaches is influenced by the mechanism of precipitation of the walls and the processes of waves and rivers.Keywords: distribution, sediment, grainsize, geochemical, XRF, beach sediment.

Characteristics of Grain Size Distribution on Beaches Sediment of Sumba Island, Nusa Tenggara Timur Based on Grainsize and Geochemical Data

Study of beaches sediment characteristics were conducted on three beaches on Sumba Island, East Nusa Tenggara.The research is a part of Widya Nusantara Expedition which conducted by using Research Vessel of Baruna Jaya VIII. The aim of this study is to determine the characteristics of coastal deposits through the observation of grain size by using the grain size trend analysis approach (Grain Size Trend Analysis, commonly abbreviated as GSTA) and geochemical analysis. A total of 36 samples were taken on each coast representing high tide, transition and low tide along the coast. A grain size analysis was performed using a Malvern Mastersizer 2000 that was processed with Gradistat 4.0 software. Geochemical analysis was carried out using X-ray fluorescence spectrometry (XRF). The distribution of beach sediments is dominated by moderate sand - coarse sand and differences on content of geochemical elements (Ca, Sr, Fe, K, and Ti). The coastal conditions that are connected to the Indian Ocean (B1) have different characteristics from the beach that connected to the Sumba strait (B5 and B7). GSTA analysis showed sediment of Laboya Beach finer than sediment on Waikelo and Melolo Beach. Geochemical elements on Laboya Beach indicates different values than others. It indicates there are differences in the provenance and composition of sediment on the all three beaches. The supply of coastal deposits on these three beaches is influenced by the mechanism of precipitation of the walls and the processes of waves and rivers.Keywords: distribution, sediment, grainsize, geochemical, XRF, beach sediment.

Rip current evidence by hydrodynamic simulations, bathymetric surveys and UAV observation

The prediction of the formation, spacing and location of rip currents is a scientific challenge that can be achieved by means of different complementary methods. In this paper the analysis of numerical and experimental data, including RPAS (remotely piloted aircraft systems) observations, allowed us to detect the presence of rip currents and rip channels at the mouth of Sele River, in the Gulf of Salerno, southern Italy. The dataset used to analyze these phenomena consisted of two different bathymetric surveys, a detailed sediment analysis and a set of high-resolution wave numerical simulations, completed with Google EarthTM images and RPAS observations. The grain size trend analysis and the numerical simulations allowed us to identify the rip current occurrence, forced by topographically constrained channels incised on the seabed, which were compared with observations.

The application of grain size trend analysis in the fine grained seabed sediment of Alexandroupolis Gulf.

Grain size trend analysis is a method that determines sediment transport direction, based on the relationship of grain size parameters (mean size, sorting, skewness). The application of the method in the seabed sediments of Alexandroupolis Gulf showed that there are three different sub areas of distinctive sediment movement of bottom sediments (water depths <40 m):(i) the eastern part, which is mainly influenced by the Evros river water/sediment influxes; (ii) the central part that is primarily controlled by the wave activity; and, (iii) the western part that is mainly influenced by the wind driven and/or thermo-saline coastal circulation.