Microplastics Transport of Microplastics

A scientific cooperation in coastal oceanography between IRD and IMER has been started in 2008 in the framework of HAIPHONG project (EC2CO, 2008-2011). Since the results of the cooperation on the start stage, the cooperation between IMER and IRD has strengthened on the others project such as BLACK CARBON, VITEL, OPCAL and promising more development in the next years. This paper presents one effect of that cooperation in the physical oceanography: some results of application a three dimension (3D) numerical model to study and assessment influences of tidal oscillation, wind and wave action on characteristics of suspended sediment transport in Bach Dang- Cam estuary (Vietnam). Measured data were collected, processed systematical, and homogeneously in order to create water river boundary condition (time-serial) for the model. Sea boundaries conditions of the model were created by NESTING method. The model (Delft3d) was setup with vertical seven layers in  coordinate. The results of mo...

Meyniana, 2001

2005: Sediment dynamics and hydrodynamics during low river discharge conditions in Nha Trang Bay, Vietnam. (Sedynamik und hydrodynamik während niedrigwasser Perioden in Nha Trang Bay, Vietnam).-Meyniana, 57:117-132, 8 fig., 1 tab., Kiel.

Tropical Aquatic and Soil Pollution

The study was carried out in Semarang City, Central Java, Indonesia, along the East Canal Flood River. There are several community activities that produce some pollutants and total suspended solids (TSS) was one of the elements is. The river transports these pollutants to the estuary. These coastal regions provide exceptional life support for creatures. This study attempts to determine the concentration value of suspended solids, its suitability to the pollution threshold value, and the distribution pattern of the sediment suspension based on hydrodynamic parameters, using the Delft3D program. This study estimated the distribution of sediment suspensions by not only describing conditions at a single point in time, but also representing seasonal conditions periodically. The concentration ranges between 0.04 kg/m3 and 0.06 kg/m3, making it good for aquaculture, marine tourism, and conservation. At high tide, the dispersion of suspended sediment leads to the land; at low tide, it leads...

Environmental Modeling & Assessment, 2010

The Danshui River estuarine system is the largest estuarine system in northern Taiwan and is formed by the confluence of Tahan Stream, Hsintien Stream, and Keelung River. A comprehensive one-dimensional (1-D) model was used to model the hydrodynamics and cohesive sediment transport in this branched river estuarine system. The applied unsteady model uses advection/dispersion equation to model the cohesive sediment transport. The erosion and deposition processes are modeled as source/sink terms. The equations are solved numerically using an implicit finite difference scheme. Water surface elevation and longitudinal velocity time series were used to calibrate and verify the hydrodynamics of the system. To calibrate and verify the mixing process, the salinity time series was used and the dispersion coefficient of the advection/dispersion equation was determined. The cohesive sediment module was calibrated by comparing the simulated and field measured sediment concentration data and the erosion coefficient of the system was determined. A minimum mean absolute error of 4.22 mg/L was obtained and the snapshots of model results and field measurements showed a reasonable agreement. Our modeling showed that a 1-D model is capable of simulating the hydrodynamics and sediment processes in this estuary and the sediment concentration has a local maximum at the limit of salinity intrusion. Furthermore, it was indicated that for Q 50 (the flow which is equaled or exceeded 50% times), the turbidity maximum location during neap tide is about 1 km closer to the mouth compared to that during spring tide. It was found that deposition is the dominant sediment transport process in the river during spring–neap periods. It was shown that, while sediment concentration at the upstream depends on the river discharge, the concentration in the downstream is not a function of river discharge.

Jàmbá Journal of Disaster Risk Studies

Continental Shelf Research

The estuaries and coastal zones of the Vietnamese Mekong Delta located at the end of the Mekong Basin are susceptible to a large variety of natural threats and human interventions such as upstream dam construction, climate change and sea level rise. In this study, we investigated sediment dynamics and morphodynamic changes in the Mekong estuaries and coastal zone, using a well-calibrated Delft3D-4 model for a 10-years period simulation. For the first time, the impacts of different drivers were distinguished to guide future adaptation strategies and policies. Our investigations pointed out that the influences of upstream sediment reduction and large-scale sand extraction would cause substantial modifications in the subaqueous delta region. Besides human-induced impacts, modeling results also showed that the sediment volume and spatial distribution changed through the simulated period according to monsoonal variation. The influence of each driver, however, not only varied in space but also time. In the flood season, the Mekong and Bassac Rivers provided a large amount of sediment (more than 90%) that was deposited on the delta front due to coastal processes. The sediment quantity transported along the coastline changed with the monsoon and was in a dominantly southwest direction due to the northeast monsoon, especially in November, December and January. As a natural process, in the estuarine region, erosion and deposition occurred alternately, but the southwest coast region (belonging to the Ca Mau peninsula) was dominated by erosion. This is because of the formation of sand bars in front of the Bassac estuaries, which influences the capacity of sediment transportation to the southwest. Consequently, navigation capacity will reduce significantly in the estuaries and coastline erosion in the Ca Mau peninsula leads to substantial loss of houses and assets of local people. Urgent actions such as stopping sand mining or modifying dam designs are needed to sustain the delta coastline.

The Thi Vai main river in South Vietnam flows from the Ba Ky weir about 37 km before entering the East Sea and is strongly affected by the tide. Its catchment, located in the provinces Dong Nai, Ba Ria-Vung Tau and Ho-Chi-Minh City, covers approx. an area of 625 km². A lot of industries are situated in this catchment.

2020

This study aims to model the distribution pattern and stratification of water mass structures by the influence of hydrodynamics using a two-dimensional numerical model. Data recording was performed in spring tide and neap tide conditions for 18 days at the Stuary Jeneberang River in Makassar. 2D numerical models with flexible mesh bases are used in this study. This model can configure the coastline and bathymetry and applied in the estuary. Model validation shows the error rate of water level elevation at stations 1 and 2 of 2.26% and 5.47%. Likewise, the model validation of the measurement results of current, u-velocity of 9.7% and v-velocity of 4.8%. The simulation results show the pattern of salinity and temperature distribution follows the flow pattern so that it affects the distribution of the structure of water mass in the estuary waters of the Jeneberang River. The interaction that occurs between the mass structure of water with the hydrodynamic factor results in a moving cur...

International Journal of Remote Sensing and Earth Sciences (Denpasar), 2010

The 3D-numerical model has been applied to simulate the current circulation and cohesive sediment transport in the Jakarta Bay, Indonesia. Sediment load comes from 3 river mouths i.e. Angke River, Karang River, and Ancol River. The model was simulated to analyze the effect of tidal current and river discharge. A constant westerly and easterly wind was used as input of the model to see the influence of monsoonal season. The numerical results showed that the tidal current flows from east to western part of the bay during ebb tide and vice versa during flood tide. The surface current circulation was dominantly influenced by the tidal current compared with the wind and river discharge effects. High turbidity level was found near the river mouths with the range of 50 to 100 mg/l. This high sediment concentration was caused by the effect of sediment load from the river upstream. In the offshore area of the bay the sediment concentration decreases up to 10 mg/l. The movement of sediments followed the current circulations. During the flood tide, the sediment concentration from the mouth of Angke River moved to the western part of the bay. Model simulated for increasing the river discharge into two times showed that the sediment distributed to the offshore direction two times longer compare with the normal debit. The transport of sediment from the Angke and Karang Rivers to the offshore area reached > 6 km, while it just reached + 2,5 km from the Ancol River .

Diacritics, 2008

In sixteenth-century South India, the notion of the imagination was strongly thematized as perhaps the defining aspect of the human mind. We examine one striking example, an allegorical play called the Bhāvanā-puruṣottama (“The Marriage of Imagination and King Best”) by Ratnakheṭa Srinivasa Dīkṣita. Here we see a king searching frantically for his own imagination, the young woman Bhāvanā with whom he is in love, while she, for her part, is absorbed in the uneven and rather frustrating processes of imagining him. The two lovers could be said mutually to determine one another’s existence. On the other hand, imagination, for this poet, is not a matter of discovering something new but of perceiving something that is already there and, by perceiving it, enhancing or intensifying its presence and its activity. At the same time, the imagination focuses on singularities, however elusive: in this period, the general faculty of imagination has become a highly personal matter.