Direction Of Sediment Transport Research Articles

Analysis of Downstream Sediment Transport Trends Based on In Situ Data and Numerical Simulation

This study conducted an in-depth analysis of the sediment dynamics in the lower reaches of the Changhua River and its estuary on Hainan Island. Through field collection of topographic data and sediment sampling, combined with advanced computational techniques, the study explored the transport pathways and depositional patterns of sediments. The grain size trend analysis (GSTA) method was utilized, in conjunction with the Flemming triangle diagram method, to classify the dynamic environment of the sediments. Furthermore, hydrodynamic modeling results were integrated to further analyze the transport trends of the sediments. The study revealed that the sediment types in the research area are complex, primarily consisting of gravelly sand and sandy gravel, indicating a generally coarse sedimentary environment in the region. The sediments in the lower reaches of the Changhua River generally transport towards the south and southwest (in the direction of Beili Bay). The net sediment transport directions inferred from the GSTA model are largely consistent with the Eulerian residual flow patterns, especially in the offshore area, where discrepancies are observed in the nearshore zone. The nearshore transport is influenced by the combined effects of alongshore currents, residual flows, and river inputs, while the offshore transport exhibits a shift from the northwest to southwest directions, reflecting the regional circulation patterns.

Shoreline Behavior in Response to Coastal Structures: A Case Study in Haikou Bay, China

The rapid development of coastal structures on sandy coastlines raises concerns about their impacts on the shoreline’s evolution and the sediment transport dynamics. This study utilized a numerical modeling approach to simulate the multi-year response of Haikou Bay’s coastline to various nearshore structures, including piers and a large artificial island. The LITLINE module of the MIKE21 (v2020) software was employed to analyze the sediment transport patterns across three distinct coastal segments. The simulation results indicated that the sediment transport directions varied significantly: from west to east in the western segment, from east to west in the middle segment, and convergence toward the center in the eastern segment, divided by a construction trestle. The net sediment transport rates were quantified as 2000 m3/year for the western segment, 8000 m3/year for the middle segment, and 13,000 m3/year (west) and 10,000 m3/year (east) for the eastern segment. Due to the conflicting sediment transport directions on each side of the breakwater, noticeable deposition occurred on both sides. The presence of the artificial island created notable deposition in its wave shadow area, while the overall impact on the shoreline changes diminished over time. These findings underscore the significant influence of human activities, particularly coastal structures, on the natural evolution of shorelines.

Evolutions of hydrodynamics and sediment transport pattern in the Qiantang Estuary (China) in response to multidecadal embankment constructions

Since the late 1960s, large-scale coastal embankments have been constructed along the Qiantang Estuary (QE, China) covering both the Qiantang River (QR) and the Hangzhou Bay (HZB) to reduce the tidal prism and thus stabilize the channel. While most previous studies have reported their relevant impacts on hydrodynamic and sediment transport in the HZB, a more comprehensive investigation covering the whole QR + HZB system remains lacking, so as a quantitative analysis of the tidal prism and the channel stability. Therefore, numerical case studies have been conducted to examine evolutions of hydrodynamics and sediment transport of the QR + HZB system in response to different coastal embankments (i.e., no embankment as in 1958; QR embankment as in 1984; QR embankment + part of HZB embankment as in 2004; both QR and HZB embankment as in 2016). It is shown that the flood tidal asymmetry in the QR and the tidal range in the HZB are significantly increased, implying an intensified tidal distortion and thus a strengthened river role after embankments. While this intensification does not change the direction (from HZB to QR) of the net sediment transport, all of the sediment exchange rates [e.g., the landward (during flood tides) and seaward (during ebb tides) sediment transport volumes, as well as the net sediment transport rate between them] exhibits obvious decreasing trends. In addition, strong deposition is observed in the Jianshan (JS) reach, which has led to further increase of the underwater giant sandbar. The constructions of embankments have facilitated the initial goal of reducing tidal prism in most part of the QR + HZB system, except some local parts of the HZB, where increased tidal prism can be observed as the effect of the enlarged tidal range overwhelms that of embankments. Moreover, the channel stability was greatly improved as the mainstream has been mostly converged to the reach centerline and the width-depth ratio of the channel has been considerably reduced. The present investigation of the QE regulation could be indicative for the management of other estuaries in the world.

Climate controls on longshore sediment transport and coastal morphology adjacent to engineered inlets

Coastal jetties are commonly used throughout the world to stabilize channels and improve navigation through inlets. These engineered structures form artificial boundaries to littoral cells by reducing wave-driven longshore sediment transport across inlet entrances. Consequently, beaches adjacent to engineered inlets are subject to large gradients in longshore transport rates and are highly sensitive to changes in wave climate. Here, we quantify annual beach and nearshore sediment volume changes over a 9-yr time period along 80 km of wave-dominated coastlines in the U.S. Pacific Northwest. Beach and nearshore monitoring during the study period (2014–2023) reveal spatially coherent, multi-annual patterns of erosion and deposition on opposing sides of two engineered inlets, indicating a regional reversal of longshore-transport direction. A numerical wave model coupled with a longshore transport predictor was calibrated and validated to explore the causes for the observed spatial and temporal patterns of erosion and deposition adjacent to the inlets. The model results indicate that subtle but important changes in wave direction on seasonal to multi-annual time scales were responsible for the reversal in the net longshore sediment transport direction and opposing patterns of morphology change. Changes in longshore transport direction coincided with a reversal in the Pacific Decadal Oscillation (PDO) climate index, suggesting large-scale, multi-decadal climate variability may influence patterns of waves and sediment dynamics at other sites throughout the Pacific basin.

Evidence for littoral convergence and sediment delivery to Mattole submarine canyon, Northern California

At geologic timescales, a significant proportion of the sediment eroded from continents is transferred from rivers to littoral cells, then through submarine canyons to deep ocean basins. Accumulation and occasional discharge of sediment from canyon headwall regions is a likely driver for the sediment gravity flows believed to be responsible for much of this mass transport, but the responsible mechanisms and event timescales in canyon heads are imprecisely defined, largely due to the drowning of canyon heads since the last glaciation and the resulting dearth of modern depositional environments to observe. We investigated a littoral cell adjacent to Mattole submarine canyon in Northern California to better understand the influence of bathymetry and coast shape on sediment trajectories and hypothesize that canyon heads promote littoral sediment accumulation due to bathymetric sheltering of the adjacent coast from waves and convergence of littoral cells exposed to varying wave direction. The uppermost gullies of Mattole Canyon extend to the littoral cell, and a train of sediment waves within the uppermost thalweg of Mattole Canyon suggests that gravity-driven flows of shore-derived sediment may have recently occurred. Mattole Canyon and nearby Mendocino Canyon flow into the deep Mendocino Channel, which has the highest observed Late Holocene sediment accumulation rates in Northern California. We documented the beach slope, grain size, and sediment provenance along 15 km of coast adjacent to Mattole Canyon and conducted numerical wave modeling to infer the dominant direction and magnitude of sediment transport, relative wave sheltering by bathymetry, and estimated sediment mobility in the vicinity of the canyon head over a multi-year period. South of the canyon headwall, in the vicinity of the Mattole River outlet, coarser sediment rich in metasandstone clasts and steeper beach slopes coincide with decadal-scale beach accretion. North of the canyon head, sediments are generally finer, beaches are flatter, clast lithologies include more quartz and mudstone grains, and there is decadal-scale net erosion. Wave modeling suggests the Mattole headwall region is subject to sustained sheltering from waves due to canyon bathymetry, littoral sediment convergence above the canyon head for much of a typical year, and occasional bed entrainment of sediment in the canyon’s uppermost gullies by large waves. Larger winter waves from the northwest likely result in net southerly drift north of the canyon head, with a high likelihood of preferentially transporting fine-grained, more quartz-rich sediment towards the Mattole headwall. Smaller summer swells from the west and south likely results in net northerly transport of metasandstone clast-rich Mattole River-derived sediment towards the canyon head. The imbalance in seasonality in wave conditions, coast shape, and sediment delivery by the Mattole River and other coastal creeks is broadly consistent with the spatial patterns in grain size, mineralogy, slope, and beach width that we observe in the vicinity of the canyon, and the net delivery of sediment to the Mattole Canyon head. An approximate mass balance of sediment flux from coastal streams feeding Mattole River littoral cell suggests that sediment volumes likely accumulate in the canyon headwall region that could supply several density flow events in a typical decade. These findings highlight the importance of the connectivity of the canyon to the nearshore region for the processes and products in canyons and fans. We hypothesize that feedbacks between canyon bathymetry, sediment accumulation, and mass evacuating flows promotes the long-term persistence of canyon systems.

Numerical investigation of grain size effect on velocity-skewed oscillatory sheet flow

Wave-induced sheet flow leads to intense sediment transport. Fine sand and medium/coarse sand exhibit opposite directions of net sediment transport under velocity-skewed oscillatory sheet flows. A newly developed two-phase mixture model is employed to simulate the sediment transport under these conditions. The model accounts for particle stress, two-phase momentum exchange, and turbulence modulation. The effects of grain size on flow characteristics and sediment transport are primarily investigated. The model effectively reproduces the spatial and temporal distributions of two-phase velocities and sediment concentration as well as the periodic distribution of erosion depth. Comparisons between configurations with medium and fine sand demonstrate that the grain size impacts sediment transport in two main ways. First, the grain size influences the periodic variations in erosion depth and the quantity of suspended sediment. A decrease in the grain size increases the phase residual and phase lag, enhancing offshore sediment transport. Second, suspended sediments modulate the flow dynamics within the oscillatory boundary layer. Through the mobile bed effect and density stratification, the grain size affects two-phase velocities, turbulence, and net sediment transport.

Architecture and dynamics of Precambrian linear megadunes: Galho do Miguel Formation, Mesoproterozoic, South-East Brazil

Recognizing the deposits of linear megadunes in ancient aeolian successions is challenging when the original bedform topography is not preserved. The present study provides a detailed analysis of the depositional architecture of an ∼ 80 m-thick interval of the Mesoproterozoic Galho do Miguel Formation (SE Brazil) to reconstruct the original morphologies of linear megadunes and to understand their dynamics. The depositional architecture reveals compound cross-bedded sets, which transition laterally into thick low-angle cross-stratified sets and planar-parallel sandstone beds. The depositional features indicate the presence of complex megadunes separated by adjoining wide dry inter-megadune areas, which were themselves flooded seasonally by a water table that rose above the depositional surface. Linear megadunes experienced two phases of development: vertical accretion and subsequent episode of lateral migration. During the vertical accretion phase, high sediment supply, typical of Precambrian aeolian systems, and the convergence of winds from two distinct directions promoted high rates of megadune growth, bedform elongation, and the formation of superimposed dunes. The lateral migration phase was characterised by a component of lateral bedform shift relative to the main along-crest sediment transport direction; this prevented preservation of a bimodal pattern of dune cross-strata azimuths. The accumulation of these deposits occurred via a combination of megadune climbing that occurred with progressive rise of the water-table level. The water-table rise hindered cannibalization of the lower parts of the migrating megadunes, allowing the accumulation and subsequent preservation of megadune sandstone packages. The rise of the water table was also responsible for the accumulation of thick dry inter-megadune strata. The unusual thickness of linear megadune and inter-megadune deposits of the Galho do Miguel Formation, as compared with Phanerozoic examples, are attributed to the interplay between the barren conditions of the early Earth, the morphodynamics of the linear megadunes, and the seasonal impact of the water table at the accumulation surface. Without a water-table control, opportunities for megadune accumulation and preservation were likely limited in Precambrian ergs.

Modeling of sediment transport direction affecting Failaka island marina bathymetry, Kuwait

Failaka Island has a marina, which was constructed in 1979 and managed by the Ministry of Communication (MOC) in collaboration with Touristic Enterprises Company (TEC). The marina is widely used for its ferry landing facility. The coastal waters around Failaka are turbid, and current velocities tend to be as high as ∼0.5 m/s during spring tide. The marina basin, with axial plane view and dimensions of about 285m by 260m, experiences shoaling of naturally flocculated fine (cohesive) sediment and coarse sand at the entrance of the channel and more generally in the southern half of the basin. Particularly noteworthy is its heavy shoaling zone along the inner side of the south breakwater close to the entrance. The Failaka island marina is suffering from siltation and sediment deposition issues. The study was carried out numerically to assess the annual sedimentation, sediment direction, and longshore current from different locations around the marina and recommend solutions to reduce the siltation and sediment deposition based on sediment transport direction at the marina entrance. The study shows that the sediment is mostly transported to the Failaka marina entrance from the southeast due to wave action. The cumulative sediment transport for the period 2016 to 2020 as depicted from locations 1 and 2, which are vulnerable to the southeast waves, is 9,164 m3 and 12,323 m3. The annual sediment transport direction affecting the marina is oriented from south to north due to wave action.

Assessing shoreline dynamics over multiple scales on the northern Yucatan Peninsula

Coastal erosion is critical in many locations along the northern Yucatan Peninsula. The area is characterized by a micro-tidal regime and low-energy wave conditions, with a high-incidence angle with respect to the shoreline. Port and harbor infrastructure for fisheries, commercial, and tourist activities has promoted the growth of coastal communities settled on barrier islands. However, the human settlements have degraded the coastal ecosystems and interrupted the littoral transport. Due to coastal development in the region, the land use of the remaining pristine coastal areas is expected to change in forthcoming years. Thus, understanding coastal changes occurring along the northern Yucatan Peninsula is fundamental for improving coastal planning. We employed open access remote sensing data sets and reanalysis information to investigate shoreline changes at different spatial and temporal scales. Shoreline position was obtained along a 150-km stretch of coast from satellite imagery using CoastSat. Firstly, reanalysis and satellite-derived information were validated with in situ measurements in the vicinity of coastal structures. A satisfactory agreement was found for characterizing the forcing conditions (waves and sea level) and shoreline evolution at different temporal scales. A dominant direction of alongshore sediment transport (50,000–80,000 m3/year) make the shoreline highly sensitive to any nearshore disturbance. We found that coastal erosion occurred in 50% of the analyzed transects, whereas beach accretion occurred in only 30%, suggesting net beach losses. Erosive trends are strongly correlated with the presence of coastal structures. The 6-km long Progreso pier induced significant beach erosion along O(10) km, while sheltered harbors induced downdrift erosion along O(1) km. Detached breakwaters and groins have an overall negative impact on downdrift areas (O(100) m). On the other hand, significant erosion was also observed in pristine areas located downdrift of a coastal lagoon due to the sediment impoundment associated with the growth of a sand spit. Moreover, shoreline sand waves drive 40-m shoreline oscillations and propagate (alongshore) at a rate of 300 m/year. The generation of sand waves seems to be related to both natural and anthropogenic perturbations, in combination with the high-incidence wave angle. Their propagation plays a key role in the shoreline dynamics of this region.

Identification of the Sediment Movement Mechanism via Grain Size and Shape: A Case Study of a Beach in Eastern Hainan Island in South China

This paper used dynamic image analysis (DIA) to analyze the grain size and shape data of beach surface sediments in Bao’ding Bay, eastern Hainan Island, China, and explored the effects of sediment transport modes and beach morphology on the grain size–shape trend curves. This paper adopted a method of combining grain size cumulative frequency curves and grain size–shape trend curves to identify three sediment transport modes: suspension, saltation, and traction, and analyzed the characteristics of the grain size–shape trend curves under different beach morphologies (reflective, intermediate, and dissipative). This paper found that the grain size–shape trend curves can effectively indicate the sediment transport modes and improve the accuracy of subpopulation division; the grain size–shape trend curves showed different distribution characteristics in the cross-shore and longshore directions, which are closely related to the beach’s morphology and sediment transport direction. This paper provides a new method and idea for studying beach sediment transport and sedimentary environment using sediment grain size and shape data.

NEOPROTEROZOIC DIAMICTITES OF THE MIDDLE TIANSHAN, KYRGYZSTAN: AGE, DEPOSITIONAL ENVIRONMENTS AND PROVENANCE

With the aim to improve our understanding of the age and genesis of the Neoproterozoic diamictites of the Middle Tianshan of Kyrgyzstan, we studied the late Precambrian strata of the Sandalash, Talas and Chatkal Ranges. The results of detrital zircon dating indicate that diamictites were deposited in the Cryogenian and Ediacaran. Diamictites in the lower part of the Shorashu Formation comprise tillites and were likely deposited during the Marino glaciation ca 640–635 Ma. Diamictites in the upper part of the Shorashu Formation represent debris flows and grain flows associated with turbidites and, apparently, have non-glacial origin; their age is not older than the early Ediacaran 616 ± 7 Ma. The pinching out of the Shorashu Formation to the north and the predominantly southerly directions of sediment transport in turbidites indicate that a non-depositional uplift located north of the basin. The distributions of detrital zircon ages in the studied samples are characterized by large peaks at 0.7–0.8 and 1.8–1.9 Ga and small peaks at ca 2.4–2.5 Ga and are almost identical to the age distributions in the Proterozoic sediments of the Tarim Craton. Comparison of the studied strata with key sections of the Kuruktag Range in the NE Tarim suggests that the diamictites of the lower part of the Shorashu Formation are analogues of late Cryogenian Tereeken tillites, and the slope facies of the upper part of the section are analogues of the early Ediacaran turbidites of the Zhamokti and Yukkengol Formations.

Multi-index assessment of sea bottom sediments of the Izmir Gulf, Aegean Sea: A study of interrelation between anthropogenic and hydrodynamic effects

This study aimed to investigate the sediment transport pathways and geochemical parameters in the Izmir Gulf to determine the heavily impacted areas by natural and anthropogenic parameters. The grain size trend analysis was used to determine sediment transport patterns and, statistical methods were employed to identify the sources and distribution of chemical elements in sediments. The main factors that were affecting the area were identified as lithogenic, anthropogenic, maritime traffic, biogenic and shipyard activities. The tannery industry (Cr), maritime traffic and shipyard/dock activities (Cu and Zn), road traffic run-offs (Pb and Zn), and untreated domestic waste discharges (TOC and S) were identified as the sources of metals. Contamination rankings based on metal concentrations indicated higher pollution levels in the Inner Gulf compared to the Central Gulf. Zinc and chromium were found to pose significant risks to benthic organisms. The pollutants tended to accumulate in deposition zones, following sediment transport directions.

Sediment transport trend and its influencing factors in coastal bedrock island sea areas-a case study of Chudao island, China

Coastal bedrock islands sea areas have a unique natural environment, frequent human activities, and complex sedimentary dynamic processes. In this paper, we select the Chudao Island sea area off the coast of Shandong Peninsula, China, as a typical research area to investigate the sediment transport trends and influencing factors by means of high-precision bathymetric survey, high-density sediment sampling, grain-size trend analysis and hydrodynamic numerical modeling. Results and analysis indicate that the grain size parameters including mean grain-size, sorting coefficient and skewness are zonal distributed, roughly parallel to the isobaths. While the overall sediment transport trend is from island shore to sea, with several convergence centers near the loop centers of bottom flow and at the edge of the agriculture area. The near-bottom flow velocity is primary factor that controlling the significance of sediment transport trend, while the flow decides the general patterns of sediment transport trend and sediment distribution. Submarine topography can either directly transport sediments down its slope, or indirectly affect the direction of sediment transport by constraining the near-bottom flow from shallow to deep waters. Besides the natural factors of bottom flow and submarine topography, human activities represented by aquaculture also affect the sediment transport trend in coastal bedrock island sea areas. First, the increased sedimentation rate caused by organic matters and the diffusion of scallop fragments may cause sediment coarsening. Second, the artificial aquaculture facilities can reduce flow velocity and therefore hinder the initiation, suspension and transport of sediment near the aquaculture areas. Our methods and findings provide high-resolution details to insight into the sediment transport trends to improve the understanding of the modern sediment dynamics in small-scale coastal bedrock island sea areas and provide reference for corresponding engineering and agriculture activities.

Comparison of Grain Size Trend Analysis and Multi-Index Pollution Assessment of Marine Sediments of the Gülbahçe Bay, Aegean Sea

In this study, 46 elements plus total carbonate and total organic carbon contents were measured in 48 sea bottom sediments to determine the pollution levels in the study area and their source to understand better the natural and anthropogenic processes in the study area. Also current flows and sediment transport pathways inferred using multidisciplinary methods by interrelation between grain size trend analysis, shallow seismic and acoustic doppler current profiler analysis to unravel the hydro-sedimentary processes in a micro-tidal environment. Four main factors that were affecting the study area were identified as lithogenic factor (50.6%) anthropogenic factor caused by untreated domestic waste (13.2%), anthropogenic factor caused by marine traffic/port activities (9.3%) and anthropogenic factor caused by small-scale industrial activities (with 6.9% of the total variance). The main source of metals in the study area were determined as untreated domestic waste discharges (total organic carbon and sulfur), maritime traffic/harbor activities (copper and zinc), and discharges of other wastes caused by urbanization. The main metal element that poses the most significant risk for benthic organisms was determined as nickel in the study area. All environmental indices showed non to moderate pollution existing in Gülbahçe Bay. It has been observed that most prominent feature of the distribution of elemental concentrations and assessment of pollution indices were that the pollutants carried inwards to Gülbahçe Bay from Izmir Central Bay with inflows, following the sediment transport directions.

A new approach to mapping littoral cells within a tide-dominated embayment

Western Port is a large tide-dominated embayment located 75 km east of Melbourne, Victoria that is flanked by a rapidly growing population, significant industrial infrastructure, grazing lands and protected RAMSAR habitats. Remarkably little is known about the sediment dynamics of Western Port despite concerning rates of erosion of the swamp and floodplain deposits including cohesive clay cliffs that fringe the sunkland. As in other tide-dominated systems, sediment dynamics in Western Port are complicated by strong tidal currents, multiple sediment sources and complex circulation. We applied the coastal sediment cell framework to Western Port, in conjunction with high resolution satellite derived rates of coastal change to elucidate sediment sharing among the sub-embayment beaches. Using end member modelling of 20 sediment assemblages based on elemental and mineralogical composition we robustly identified seven end members that correspond to different point and diffuse provenances. Hierarchical clustering of the 20 beaches dispersed across the bay yielded nine coastal cells, delimited by headlands, deep water channels, estuaries or disruptive infrastructure. Analysis of shoreline change within the cells suggests most cells are neutrally or positively balanced but a northward movement of sediments is leading to rotation. The deep channels provide a pathway for Bass Strait sediments to bypass the embayment headlands and tidal currents enable cross shore exchange with the channels beyond wave derived closure depth in some locations. Understanding the sediment cell boundaries and direction of sediment transport can assist with the management of erosion hotspots; the novel approach applied here can resolve complex connected coastal systems such as estuaries and embayments.

Change of sediment transport direction within the Rio Jaguaribe estuary, NE Brazil, by means of clay mineralogical analyses

The estuary of the Rio Jaguaribe (NE Brazil) is filled by a sediment sequence of more than 23 m and characterised by estuarine plains that – today - extend 30 km upstream.We investigated the sedimentary dynamics in the Rio Jaguaribe estuary since the early Holocene by means of clay mineralogical analyses, as well as sediment analyses from 11 sediment cores. The clay mineralogical approach proves to provide the most robust results. A transition of the illite/kaolinite peak area ratio from 0.3 to 1.8 within the vertical depositional record suggests a change of sediment transport direction over time. Whereas in the lower sequence marine influence dominates, characterised by the relatively high kaolinite content originating from the weathered Barreira formation at the coast, in the upper sequence sediments of fluvial origin dominate, which are characterised by the relatively high illite content originating from the crystalline rocks in the source area of the Jaguaribe river. The depositional architecture of the Holocene sediments of the Jaguaribe estuary shows a seawards prograding infill, assumed to have occurred since the mid-Holocene and supports studies suggesting a stagnating or slightly falling relative sea level (RSL) since ∼7000 BP.

Sediment Budget and Net Sediment Transport on a Coast Dominated by Waves and Offshore Currents: A Case Study on the Ishikawa Coast and Its Surrounding Areas in Japan

This study discusses the coastal sediment budget for the Ishikawa coast using 12 years of observational datasets; it involves an understanding the local and regional sediment dynamics, the intensity of the transport processes in the region, and sediment supply from a local river. Although alongshore sediment transport and sediment budgets have been analyzed in previous studies, only a few conducted cross-shore sediment transport evaluations. The concentration of suspended sediments will be determined in this study, taking into account the influence of waves that are associated with the coastal current. The cross-shore sediment transport using sediment budget analysis indicated that the net alongshore sediment transport directions in the surf and offshore zones are opposite on the Ishikawa coast. The increase in the sediment budget of the surf zone can be attributed to the river sediment supply and longshore sediment transport inflow. Because of the significant outflow components of longshore and cross-shore sediment transports, the offshore zone budget showed a decreasing trend. A detailed sensitivity study was performed by varying the input parameters, in order to determine the possible ranges of net transport rates and sediment transport to the adjacent coasts. The results demonstrated the possibility of a clockwise residual sediment circulation. Our method can be used to analyze the alongshore sediment transport for other coasts and supplement future studies on coastal sedimentology and sediment budgets.

STUDY OF WAVE DOMINANT DIRECTIONS ON SEDIMENT TRANSPORT IN THE ESTUARY OF KAPUAS RIVER, PONTIANAK, WEST KALIMANTAN

The Kapuas River is a very important water transportation route in West Kalimantan, crossing 5 districts and 1 city. The problem that occurs in the shipping lane on the Kapuas River is the accumulation of severe sediment at the mouth of the estuary. This becomes an obstacle for ships with large loads to sail, for this reason, this research was carried out. The purpose of this study was to determine the dominant direction of waves and sediment transport. This study was calculated using the CERC (Coastal Engineering Research Centre) method and using secondary data. It was found that the dominant wave direction came from the North (N) direction with an incidence percentage of 22.496%. Percentage of occurrence from the Northwest (NW) direction is 12.145%, from the West (W) direction is 6.253%, and from the Southwest direction (SW) is 11.724%. While the amount of sediment transport from the Northwest is -393062.1306 m3/year with the characteristics of the sediment being clay, from the West it is -250.1672 m3/year with the sediment characteristics being silty clay and from the Southwest, it is 579090.2782 m3/year with sediment characteristics of silty clay. The results of the sediment calculation have negative results which indicate that there is no sediment transport from the Northwest and West, but the sediment is deposited. For this reason, it is necessary to carry out appropriate handling of these problems to reduce sediment build-up in the study area.

Application of artificial neural network and seismic attributes to predict the distribution of Late Oligocene sandstones in the Cuu Long basin

Artificial neural network (ANN) has been widely applied in oil and gas exploration and production. This study presents the results of predicting the distribution of Late Oligocene sandstones in the Cuu Long basin based on the application of ANN and seismic attributes. These results have great significance, helping to orient the oil and gas prospection and exploration of the Cuu Long basin and other exploration objects on the continental shelf of Vietnam. The authors used unsupervised neural networks (UNN) and UNN methods constantly associated with the principal component analysis (PCA) to divide seismic facies. Seismic attributes such as Root mean square (RMS), Frequency, Envelope, Relative Acoustic Impedance (RAI), Phase, Sweetness, Amplitude, and t-Attenuation were analyzed and selected as input for the ANN training and testing process. These attributes can reflect changes in lithology, and sedimentary facies, from which will have a better view of the distribution of reservoirs in the study area. From 4 to 10 classes of seismic facies have been tested using each method to improve the results. Comparing the results of seismic facies classification by the UNN method and by UNN combined with PCA, it can be seen that the UNN combined with PCA will help reduce noise in seismic data better than UNN only. The research results have identified the distribution of Late Oligocene potential sandstones in the study area in the Cuu Long basin, which are mainly concentrated on the slopes of a large lake, with the direction of sediment transport from the West and Northwest.

Microclimate and Wind Regime of Three Typical Landscapes in the Northeastern Ulan Buh Desert

Knowledge of the microclimate and wind regimes of different land landscapes can be used to support natural resource development and agricultural productivity in desert areas. The aim of this study is to provide a theoretical basis and technical support for the management of Ulan Buh Desert Oasis and the comprehensive prevention and control of sandstorms from the surrounding desert in northern China. We examined the microclimate and wind regime of three landscapes—desert, desert–oasis ecotone, and oasis—and discussed the factors underlying the observed variations. Similar patterns were found in annual temperature, annual relative humidity, and wind speed between the desert, desert–oasis, and the oasis. Compared with the desert and the desert–oasis ecotone, the average annual temperature and wind speed in the oasis were lower by 2.56%–5.38% and 32.99%–37.05%, respectively. Average annual relative humidity in the oasis was higher than in other areas by 1.31%–2.57%. The desert, desert–oasis ecotone, and the oasis were dominated by westerly winds. Wind direction was relatively stable in the oasis and variable in the desert and desert–oasis ecotone. There were intermediate wind energy fields in the desert and the desert–oasis ecotone and a low wind energy field in the oasis. In the desert–oasis ecotone, drift potential (DP), resultant drift potential (RDP), and resultant drift direction (RDD) were 231.87 VU, 97.21 VU, and 104.33°, respectively. In the desert, DP was 228.45 VU, RDP was 92.65 VU, and RDD was 76.05°. In the oasis, the DP was 61.85 VU, RDP was 38.04 VU, and RDD was 92.97°. In the desert and the desert–oasis ecotone, sediment transport potential was the highest in spring, second highest in autumn, third highest in winter, and lowest in summer. In the oasis, it was the highest in winter, second highest in autumn, third highest in spring, and lowest in summer. There are complex variations in the dominant sediment transport directions in the desert and desert–oasis ecotone in the study area. Variations in the dominant sediment transport direction in the oasis are less complicated and are associated with the seasons. The oasis is primarily threatened by sandstorms from the south-southeast in spring.