Simulation of Ballast Water Dispersion in the Gulf of Tonkin and Offshore Waters of Hai Phong Port, Vietnam

Transfer of invasive alien organisms and their negative impacts have been recorded around the world. It is estimated that approximately 7,000 species of marine creatures are silently moved around the world by ballast water every hour. Recently, discharge of ballast water in the coastal area has become a serious concern. The movement of discharged ballast water and accompanying alien organisms largely depends on the preveiling hydrodynamics of the receiving water body. Dynamics simulation models for marine environment provide sound prediction of dispersion of ballast water. The study was undertaken in the seas of the Gulf of Tonkin and in the offshore area of Hai Phong Port using the MIKE 21 model – a two-dimensional hydrodynamics model. The yearly-mean wind field was used in the model to generate the circulation. Ballast water discharged to the three sites in the study area was simulated by using dispersal-advection model. The outputs showed that ballast water discharged near the coast tends to move along the coastline. Ballast water discharged at 200 NM seaward from the coast is still able to influence the coastal zone of Vietnam

The burden and characteristics of enteric fever at a healthcare facility in a densely populated area of Kathmandu.

Enteric fever, caused by Salmonella enterica serovars Typhi and Paratyphi A (S. Typhi and S. Paratyphi A) remains a major public health problem in many settings. The disease is limited to locations with poor sanitation which facilitates the transmission of the infecting organisms. Efficacious and inexpensive vaccines are available for S. Typhi, yet are not commonly deployed to control the disease. Lack of vaccination is due partly to uncertainty of the disease burden arising from a paucity of epidemiological information in key locations. We have collected and analyzed data from 3,898 cases of blood culture-confirmed enteric fever from Patan Hospital in Lalitpur Sub-Metropolitan City (LSMC), between June 2005 and May 2009. Demographic data was available for a subset of these patients (n = 527) that were resident in LSMC and who were enrolled in trials. We show a considerable burden of enteric fever caused by S. Typhi (2,672; 68.5%) and S. Paratyphi A (1,226; 31.5%) at this Hospital over a four year period, which correlate with seasonal fluctuations in rainfall. We found that local population density was not related to incidence and we identified a focus of infections in the east of LSMC. With data from patients resident in LSMC we found that the median age of those with S. Typhi (16 years) was significantly less than S. Paratyphi A (20 years) and that males aged 15 to 25 were disproportionately infected. Our findings provide a snapshot into the epidemiological patterns of enteric fever in Kathmandu. The uneven distribution of enteric fever patients within the population suggests local variation in risk factors, such as contaminated drinking water. These findings are important for initiating a vaccination scheme and improvements in sanitation. We suggest any such intervention should be implemented throughout the LSMC area

A Climate Change Assessment via Trend Estimation of Certain Climate Parameters with In Situ Measurement at the Coasts and Islands of Viet Nam

This study presents results on an assessment of climate change in the nearshore and coastal areas of Viet Nam through an evaluation of trends of certain climatic parameters (air temperature, sea water temperature, sea level, and number of typhoons landed at the Vietnamese coast by year) using time series data of hydro-meteorological records at the coasts and islands of Viet Nam. The method used for the trend evaluation is the Mann–Kendall test ran at the 5% significance level and Spearman rank correlation coefficient. It was found that there is an extremely likely increasing trend of air temperature for almost all observation stations at the coasts and islands of Viet Nam. However, it was unable to confirm a general trend for sea surface water temperature; except for very few stations in semi-closed waters, there is no clear trend in annual average sea water temperature at a majority of stations. Additionally, there is an extremely likely rising trend of sea level at a majority of stations with reliable data, but the rates of increase are very different for different stations. The reasons for discrepancies in the trend of annual average sea water temperature and sea level at different stations are still not understood, but it seems that an assessment of the vertical movement of the ground surface at the stations is necessary to have an accurate assessment of the rate of sea level rise due to climate change and of the influence of general circulation in the East Viet Nam Sea on the trend of sea water temperature in that location. It is also found that there is a likely decreasing trend in the frequency of typhoons landed at the Vietnamese coast; however, this trend might not be due to climate change, but to climate variability

Rational Evaluation Methods of Topographical Change and Building Destruction in the Inundation Area by a Huge Tsunami

In the case of huge tsunamis, such as the 2004 Great Indian Ocean Tsunami and 2011 Great East Japan Tsunami, the damage caused by ground scour is serious. Therefore, it is important to improve prediction models for the topographical change of huge tsunamis. For general models that predict topographical change, the flow velocity distribution of a flood region is calculated by a numerical model based on a nonlinear long wave theory, and the distribution of bed-load rates is calculated using this velocity distribution and an equation for evaluating bed-load rates. This bed-load rate equation usually has a coefficient that can be decided using verification simulations. For the purpose, Ribberink’s formula has high reproducibility within an oscillating flow and was chosen by the authors. Ribberink’s formula needs a bed-load transport coefficient that requires sufficient verification simulations, as it consumes plenty of time and money to decide its value. Therefore, the authors generated diagrams that can define the suitable bed-load coefficient simply using the data acquired from hydraulic experiments on a movable bed. Subsequently, for the verification purpose of the model, the authors performed reproduced simulations of topography changes caused by the 2011 Great East Japan Tsunami at some coasts in Northern Japan using suitable coefficients acquired from the generated diagrams. The results of the simulations were in an acceptable range. The authors presented the preliminary generated diagrams of the same methodology but with insubstantial experimental data at the time at the International Society of Offshore and Polar Engineers (ISOPE), (2018 and 2019). However, in this paper, an adequate amount of data was added to the developed diagrams based on many hydraulic experiments to further raise their reliability and their application extent. Furthermore, by reproducing the tsunami simulation on the Sendai Natori coast of Japan, the authors determined that the impact of total bed-load transport was much bigger than that of suspension loads. Besides, the simulation outputs revealed that the mitigation effect of the cemented sand and gravel (CSG) banks and artificial refuge hills reduced tsunami damage on Japan’s Hamamatsu coast. Since a lot of buildings and structures in the inundation area can be destroyed by tsunamis, building destruction design was presented in this paper through an economy and simplified state. Using the proposed tsunami simulation model, we acquired the inundation depth at any specific time and location within the inundated area. Because the inundation breadth due to a huge tsunami can extend kilometers toward the inland area, the evaluation of building destruction is an important measure to consider. Therefore, the authors in this paper presented useful threshold diagrams to evaluate building destruction with an easy and cost-efficient state. The threshold diagrams of “width of a pillar” for buildings or “width of concrete block walls” not breaking to each inundation height were developed using the data of damages due to the 2011 Great East Japan Tsunami