Coast Of Vietnam Research Articles

THE CREATION OF BIOCLIMATIC VEGETATION MAP TO DEVELOP SUSTAINABLE AGRO FORESTRY IN BA AND KONE RIVER BASIN, VIETNAM

Bioclimate and natural vegetation have a long - term relationship that identify the potential vegetation distribution at different areas. For that reason, bioclimatic classification system was applied to the territory of Ba and Kone river basin, Vietnam. The precipitation and temperature dataset of Ba and Kone river basin was collected from 17 climate, hydrology, rain gauge stations which allowed to create a bioclimatic map at a scale of 1:250.000. Three bioclimatic factors of thermal-moisture basic conditions such as annual temperature (TN), annual rainfall (RN), length of dry season (n) are selected as criteria system of Ba and Kone river basin’s bioclimate. In order to describe the relationships between bioclimatic variables and zonal vegetation units, the resulting map presented 12 bioclimatic units corresponding distribution of vegetation from low to high altitudes. By building bioclimatology map in Ba and Kone river basin, the government can develop sustainable agro forestry in Central Highlands and South Central Coast of Vietnam.

RESEARCH THE POSSIBILITY OF USING SEA SAND IN ROADBED CONSTRUCTION IN VIETNAM

Currently, the river sand is becoming depletion leading to a rise in the price of construction material and issues related to the environment such as the depth of the river bed, lowering of the groundwater and salinity intrusion into the rivers. Meanwhile, demand for construction materials increases annually due to growth in infrastructure development demand. Therefore, finding alternative material sources is an urgent problem needing to be addressed. Specifically, sea sand has many potential abilities to replace river sand and other materials in construction. The result of the study revealed that sea sand on the coast of Vietnam accommodates most of the roadbed materials requirements according to standard TCVN 9436:2012. The study has proposed a feasible method to construct the roadbed by sea sand. The results of stability analysis by Slope/W show that the roadbed using alternating filling method considerably improves the safety factor which increases on average 13.8% in comparison with the roadbed is filled by sea sand and covered by clay. In addition, a cost comparison between the roadbed constructed by the alternating method and conventional roadbed shows that using sea sand brings a significant cost saving for the project. Moreover, using sea sand as an alternative material source also has several positive effects on the environment such as utilizing, dredging ports and seabed, making use of wild dunes, reducing the amount of river sand extracted annually, minimizing the impacts of river sand exploitation.

Risk management and logistical performance: A case of the fishery supply chain north central coast of Vietnam

In any given supply chain, risks can occur, and it can reduce the performance of an entire production line. To maintain a competitive advantage, manufacturers should anticipate and manage risks. This paper aims to assess the impact of risks associated with the fishery supply chain on logistics performance. The research was conducted with 297 seafood producers on the North Central Coast of Vietnam. The study results show that risk factors such as supply risks, market risks, operational risks, environmental risks, and financial risks have a direct impact on the logistical performance of firms in the fishery supply chain. The study also proposes solutions to limit risks for businesses.

Key Factors Affecting Sustainable Tourism in the Region of South Central Coast of Vietnam

Sustainable tourism is the development of tourism activities to meet the current needs of tourists and indigenous peoples while paying attention to the conservation and improvement of resources for the development of tourism activities in the future (World Tourism Organization, 2013). With the aim of identifying factors affecting the development of sustainable tourism in the South Central Coast of Vietnam, the study conducted a typical survey of 160 tourism managers and 240 tourists traveling or have participated in tourism activities of 8 provinces in the South Central Coast of Vietnam, and used the exploratory factor analysis (EFA) analysis and regression analysis for analyzing the data. The research results show that 11 factors impact the development of sustainable tourism in the South Central Coast namely Institutions and policies for tourism development, Infrastructure, Tourism resources, Human resources for tourism, Diversity of tourism services, Relevant support services, Activities of association and cooperation for tourism development, Tourism promotion and encouragement, Tourists' satisfaction, Local community, and Other factors. At the same time, among the above factors, the factors Institutions and policies for tourism development, Infrastructure, Tourism resources, and Local community strongly impact the development of sustainable tourism in the region.

Morpho-anatomical characteristics and antimicrobial activity of crude extract of Tephrosia villosa (L.) Pers. growing on sandy soil of Phan Thiet City, Binh Thuan Province, Vietnam

Tephrosia villosa (L.) Pers. is an herb species distributed mainly in arid sandy lands of the South Central Coast of Vietnam, including Binh Thuan province. The existing Vietnamese folk remedies have mentioned the medicinal effects of this herb in the treatment of edema and diabetes. Documents available in Vietnam provided only basic information on the morphology of this species. Therefore, this study aimed to investigate the morphological and anatomical characteristics of stems, leaves and roots of the plants in the analysis of relation to climatic conditions of the region. Antibacterial activity was initially studied as a basis for subsequent pharmacological studies. The crude ethanolic extracts were tested for inhibitory against Pseudomonas aeruginosa and Staphylococcus aureus by agar well diffusion method. The results showed that the plants had formed the morpho-anatomical characteristics to adapt to strong wind, strong light, high temperature, and dry sandy soils of the region. The ability to inhibit the two mentioned bacteria via the diameters of the halo was 10.8 – 12.7 mm, respectively. The recommendation was to continue to study the anatomical characteristics of the primary roots to complete the data and further investigate the antibacterial and antifungal activities of extracts of Tephrosia villosa.

Geological characteristics of potential geoparks in the South central of Viet Nam

The coast of South Central Vietnam from Danang city to Binh Thuan province is about 1200 km long, distributing many geological and geomorphic heritages of high scientific values, including representativeness, integrity and rarity, deserving to build a national geopark such as: i) Ly Son volcanic island geopark is formed up of volcanic materials mainly explosive in the late Holocene age; ii) Phu Yen coastal geopark possessed geological and geomorphic diversity with the presence of ancient Pre-Cambrian rocks; iii) Red Sand Plateau and Rocky Coast Ninh Thuan- Binh Thuan geopark has shaped by intrusive and extrusive igneous rock tips and characterized by majestic red sand plateau. The three geological parks will be established as a legal basis for the conservation of geological and geomorphological heritage for the research, education and local economic development.

Spatial Pattern of Construction Land Distribution in Bays along the Coast of Vietnam

Current studies of urban spatial morphology have rarely focused on the particularity of coastal cities, such as sea–land gradient features and bay types. In this paper, we provide a method to analyze the spatial and vertical distribution of construction land in the bay area and discuss the influence of bay type on the distribution characteristics. Landscape indexes and a clustering algorithm were used to identify the spatial pattern of construction land distribution. Strip division was used to analyze the landscape features of construction land in the sea–land direction. We established eight large bays in Vietnam as the study area. According to the formation and geomorphology of the bay, the eight bays were divided into five types: delta bay, lagoon bay, structural bay, bedrock erosion-stacking bay and estuary bay. The construction land data were generated from Landsat images captured in 1988 and 2015 or so. The study effectively identified five spatial patterns of construction land distribution in bays without prior knowledge. Danang Bay (a bedrock erosion-stacking bay) had a typical high intensity-high concentration pattern, and Hai Loc Bay (a delta bay) had a typical high intensity-low concentration pattern. In the sea–land gradient, the proportions of construction land in the 0–2 km zone were greatest. In Danang Bay, the proportion generally decreased in the sea–land direction; while in Hai Loc Bay, the proportion increased.

Transcriptome analysis of genes and pathways associated with metabolism in Scylla paramamosain under different light intensities during indoor overwintering

BackgroundScylla paramamosain is one of the commercially crucial marine crustaceans belonging to the genus Scylla, which is commonly distributed along the coasts of China, Vietnam, and Japan. Genomic and transcriptomic data are scarce for the mud crab. Light intensity is one of the ecological factors that affect S. paramamosain during indoor overwintering. To understand the energy metabolism mechanism adapted to light intensity, we analyzed the transcriptome of S. paramamosain hepatopancreas in response to different light intensities (0, 1.43, 40.31 μmol·m− 2·s− 1).ResultsA total of 5052 differentially expressed genes were identified in low light group (LL group, 3104 genes were up-regulated and 1948 genes were down-regulated). A total of 7403 differentially expressed genes were identified in high light group (HL group, 5262 genes were up-regulated and 2141 genes were down-regulated). S. paramamosain adapts to different light intensity environments through the regulation of amino acids, fatty acids, carbon and energy metabolism. Different light intensities had a strong impact on the energy generation of S. paramamosain by influencing oxygen consumption rate, aerobic respiration, glycolysis/gluconeogenesis pathway, the citrate cycle (TCA cycle) and fatty acid degradation.ConclusionLow light is more conducive to the survival of S. paramamosain, which needs to produce and consume relatively less energy to sustain physiological activities. In contrast, S. paramamosain produced more energy to adapt to the pressure of high light intensities. The findings of the study add to the knowledge of regulatory mechanisms related to S. paramamosain metabolism under different light intensities.

Species biodiversity and distribution of seagrass beds in several coastal areas of central Vietnam

Seagrasses provide habitat and abundant food supplies for numerous marine species and seagrass ecosystems play a vital role in protecting the coast from erosion. There were numerous seagrass studies in Vietnam, however, while these studies provide information on specific studied places, there is a lack of comparison between studies for providing a broad picture of the overall seagrass ecosystem along the coast of Central Vietnam. Hence, this study of species diversity and distribution of seagrasses along the coast of Central Vietnam was conducted to provide comparative data, which is highly valuable for the proper exploitation, management, and sustainable development of seagrass resources in Central Vietnam. This study identified eight species of seagrass belonging to two families—Hydrocharitaceae and Cymodoceaceae—in the waters around several islands in Central Vietnam. Among them Halophila beccarii in the Cua Dai estuary was listed in the Red List of Threatened Species by the International Union for Conservation of Nature (IUCN) (2017)—at risk of global extinction. The results revealed that the seagrass beds in several coastal areas of Central Vietnam have diminished over time with respect to the number of species and their distribution with causes attributed to anthropogenic activities. The seagrass canopy coverage ranged from 5 to 100% (57 ± 36.20%) near several coastal islands of Central Vietnam. The majority of seagrass is distributed in both intertidal and subtidal zones Our findings suggest that water quality and important sedimentary processes vital to ecosystem health need to be assessed throughout the coastal region.

Distribution of heavy metals in sediment along the Southern coast of Vietnam

The heavy metals (HM), particularly As, Cd, Pb and Hg, are considered most toxic to biota and environment. In this study, spatial and seasonal distribution of HMs (Cd, Pb, Hg and As) were measured in two sediment fractions (< 63 μm and 63 – 500 μm) collected in the farming area of blood cockle. A total of 104 sediment sampled along the Southern coast of Vietnam between December 2012 and July 2015 were examined. The average concentrations (μg/g) of As, Cd, Pb and Hg in sediment fraction of 63 – 500 μm ranged from 4.16 to 16.8, < 0.004 to 0.219, 9.52 to 17.3 and 0.031 to 0.076, respectively. While, the mean levels (μg/g) of As, Cd, Pb and Hg in sediment fraction of < 63 μm ranged from 4.59 to 12.8, < 0.004 to 0.187, 9.94 to 14.6 and 0.042 to 0.080, respectively. Generally, no statistically significant differences were found for concentrations of HMs in both fractions between two seasons and among provinces. The concentrations of HMs analyzed in sediment were compared to quality guidelines for the protection of aquatic life recommended by the Canadian Council of Ministers of the Environment (CCME) and the Vietnamese organizations (QCVN 43 : 2012/BTNMT). HM levels in all samples were lower than the Vietnamese regulation and the probable effect level in the CCME guideline. However, As levels in 67/103 and 84/104 of two fractions of < 63 μm and 63 – 500 μm, respectively, exceeded the threshold effect level of 7.24 μg/g in the CCME standard. It suggested that As accumulated in sediment in these provinces could be harmful to the aquatic organism.

Summertime eastward jet and its relationship with western boundary current in the South China Sea on the interannual scale

The western boundary current (WBC) in the South China Sea (SCS) flows northward in summer, closely following the Vietnam coast, and splits near 11.2° N into one eastward offshore branch named summertime eastward jet (SEJ). SEJ is significant between 110–112° E, and gradually becomes wider, shallower, weaker and warmer toward eastward until it disappears after 113.5° E. Based on the monthly mean Simple Ocean Data Assimilation (SODA) data, SEJ and its relationship with WBC on the interannual scale are studied. At the cross section 111.2° E, the current axis of SEJ (YSEJ) swings in the north–south direction with climatological value of 11.7° N and standard deviation of 0.9°, and the standard deviation of surface intensity and volume transport of SEJ (SISEJ and VTSEJ) is about 50% and 88% of the climatological value 28 cm s−1 and 4.6 Sv, respectively. In El Nino developing summers, SEJ increases its volume by 37% with 0.2° southward deviation, while in the decaying summers, SEJ decreases its volume by 43% with 0.5° northward deviation. More interestingly, SEJ has prominent correlation with the southern WBC (0.54 for VT and 0.41 for SI, > 99%), and both of them strengthen (weaken) in El Nino developing (decaying) summers. The response of SEJ and the southern WBC to El Nino can be attributed to the setting up of the anticyclonic circulation in Sverdrup balance driven by the negative wind stress curl in the southern SCS. The negative wind stress curl controls the southern WBC and further determines the transport of SEJ based on Sverdrup balance.

A Hybrid Approach Using GIS-Based Fuzzy AHP–TOPSIS Assessing Flood Hazards along the South-Central Coast of Vietnam

Flood hazards affect the local economy and the livelihood of residents along the South-Central Coast of Vietnam. Understanding the factors influencing floods’ occurrence potentially contributes to establish mitigation responses to the hazards. This paper deals with an empirical study on applying a combination of the fuzzy analytic hierarchy process (AHP), the fuzzy technique for order of preference by similarity to ideal solution (TOPSIS), and a geographic information system (GIS) to assess flood hazards along the South-Central Coast of Vietnam. Data are collected from focus group discussions (FGDs) with five communal authorities; a questionnaire completed by eight hamlet heads in the Phuoc Thang commune (Binh Dinh province); and documents, reports, and thematic maps provided from official sources. A total of 12 maps of flood factors are prepared. The results show that terrain elevation, creek-bottom terrains, high tide-induced flooding area, and distance to water body are the main factors affecting flood hazards. The An Loi hamlet faces the highest risk for floods, followed by Lac Dien, Luong Binh, and Pho Dong. The map of flood hazards indicates the western part is assessed as low hazard, whereas the eastern part is a very high hazard area. The study findings show that the hybrid approach using GIS-based fuzzy AHP–TOPSIS allows connecting decision makers with the influencing factors of flooding. To mitigate floods, both the Vietnam national government and the Binh Dinh provincial government should integrate natural hazard mitigation into socio-economic development policies.

Wave overtopping and splash-up at seawalls with bullnose

Seawalls have been erected to protect hundreds of towns and tourism areas stretching along the coast of Vietnam. During storm surges or high tides, wave overtopping and splash-up would often threaten the safety of infrastructures, traffic and residents on the narrow land behind. Therefore, this study investigates these wave-wall interactions via hydraulic small scale model tests at Thuyloi University. Remarkably, the structure models were shaped to have different seaward faces and bullnoses. The wave overtopping discharge and splash run-up height at seawalls with bullnose are significantly smaller than those without bullnose. Furthermore, the magnitude of these decreasing effects is quantitatively estimated.

Comprehensive Study of the Sand Spit Evolution at Tidal Inlets in the Central Coast of Vietnam

Tidal inlets along the central coast of Vietnam are located in a microtidal, wave-dominated coastal environment. In addition, the Vietnam coast is highly influenced by the seasonal monsoon regime, which is characterized by large northeast waves from October to March and calm southeast waves from April to September every year. Consequently, the tidal inlet entrance morphologies often suffer from a dynamic seasonal evolution due to distinct differences in the direction of wave-induced longshore sediment transport (LST) between the two monsoon seasons. The migration or closure of tidal inlets causes a lot of problems for socio-economic development in the region since these are the main reasons leading to an increase in the risk of coastal flooding and the obstruction of navigation. This paper presents a comprehensive study of the morphological evolutions of natural tidal inlets on the central coast of Vietnam using long-term remote sensing data sets and by the Delft3D numerical model. Surprisingly, the estimated LST rates from the former method are in an order of magnitude agreement with the results from the latter one for all of the areas in this study. Based on the conservation equation for sand and comprehensive data collection, a new simple empirical formula for predicting the sand spit elongation rate as a function of the sand spit width is developed. Although the breaching of sand spit might happen during an extreme flood event at some tidal inlets, the growth rate of the spit before and after the breaching is almost unchanged. These findings are very useful information for supporting the local coastal authorities to find better management solutions in terms of sustainable development.

Acrylic fibers coated with copper hexacyanoferrate to determine 137Cs activity in coastal seawater of Vietnam

A method employing 137Cs sorption to copper hexacyanoferrate (Cu2[Fe(CN)6])-coated fibers for determining 137Cs activity in seawater is presented in this paper. The Cu2[Fe(CN)6]-coated fibers were packed into a PVC cartridge and used to treat 300 L of seawater, exhibiting a 137Cs sorption efficiency of above 99%. The Cu2[Fe(CN)6]-fiber samples containing 137Cs were subsequently dried and placed into a 500 mL Marinelli beaker to determine the activity concentrations by gamma spectrometry. This method was applied to seawater of the Phuoc Dinh and Vinh Hai coastal areas in Ninh Thuan province, Vietnam. The activity concentrations of 137Cs in the surveyed areas ranged from 1.14 to 1.44 Bq/m3. The activities of 137Cs in the seawater samples of this work were compared with those observed in seawater on the coasts of Vietnam and other countries along the South China Sea.

Abnormal Strong Upwelling off the Coast of Southeast Vietnam in the Late Summer of 2016: A Comparison with the Case in 1998

The traditional view holds that a weakened upwelling has often been observed off the coast of southeast Vietnam during the post-El Niño summer. This study investigated a strong upwelling and concurrent phytoplankton bloom off the coast of southeast Vietnam in August 2016 by comparing it with another case in 1998. Analyses of the upwelling structure and formation mechanisms indicated that the abnormal strong upwelling in August 2016 was attributable to strong wind-driven offshore Ekman transport and Ekman pumping, which were caused by the accompanying southwesterly anomalies south of the anomalous cyclone (AC) over the western North Pacific (WNP), and vice versa in August 1998. This anomalous southwesterly wind associated with the AC over the WNP could not be explained by La Niña, the negative Indian ocean dipole, or the positive Pacific meridional mode events. Further analyses showed that the Madden–Julian oscillation (MJO)-induced westerly winds could have contributed more than 75% of the original zonal winds. Nine tropical cyclones generated over the WNP were favorable for excessive precipitation. The opposite configurations of precipitation patterns over the WNP and the Maritime Continent could have further strengthened the AC via a Gill response.

Future sea level rise along the coast of China and adjacent region under 1.5 °C and 2.0 °C global warming

Although future sea level rise along the China coast has been projected by various studies for different representative concentration pathways (RCPs), the projections for different warming thresholds, e.g. 1.5 °C and 2.0 °C, have not been done specifically for this region, to the best of our knowledge. We provide such a projection here based on the climate projections of Coupled Model Intercomparison Project Phase 5 (CMIP5). The projections are given for 20 tide-gauge stations along the coast of China, Korea, Japan, and Vietnam. Vertical land motion (VLM) is also estimated for stations that have tide gauge records and satellite altimetry both covering the period of 1993–2018. Local land motion (LLM) is then estimated by subtracting the land motion due to glacial isostatic adjustment (GIA) from VLM. Without considering LLM, sea level rise by 2100 at median probability is projected to be 38–49 cm relative to the average sea level over 1986–2005 under warming of 1.5 °C, and increase to 46–57 cm when the warming threshold is increased to 2.0 °C. The steric component is the main contributor to this increase in sea level. Inclusion of LLM will not affect the sea level increase between the two warming thresholds, but it will make the local sea level rise by 2100 at certain locations substantially higher (up to 36 cm) or lower (up to 13 cm).

Distribution patterns and biogeography of Sargassum (Fucales, Phaeophyceae) along the coast of Vietnam

Abstract Sargassum species form large beds that play an important role in coastal ecosystems. The beds are abundant and Sargassum is often used as food and in Asian medicine in Vietnam. As a base for future use and conservation, we surveyed 14 species of Sargassum at eight locations during April-May of 2018 and 2019. Sargassum species from Vietnam were divisible into northern and southern groups; the northern group comprised Sargassum graminifolium, Sargassum herklotsii, and Sargassum cotoense, which occur in the North and North Central zones. The southern group comprised Sargassum bicorne, Sargassum feldmannii, Sargassum ilicifolium, Sargassum swartzii, and two endemic species, Sargassum phamhoangii and Sargassum quinhonense, which occur in the Central to South West zones. Three species, Sargassum aquifolium, Sargassum oligocystum, and Sargassum polycystum, were widespread along the long coast of Vietnam. This is the first report on distribution patterns of Sargassum species along the long coast of Vietnam. Our study provides baseline data for evaluating ecological disturbance and risks of Sargassum-associated ecosystems.

The Contribution of Forerunner to Storm Surges along the Vietnam Coast

Vietnam, located in the tropical region of the northwest Pacific Ocean, is frequently impacted by tropical storms. Occurrence of extreme water level events associated with tropical storms are often unpredicted and put coastal infrastructure and safety of coastal populations at risk. Hence, an improved understanding of the nature of storm surges and their components along the Vietnam coast is required. For example, a higher than expected extreme storm surge during Typhoon Kalmegi (2014) highlighted the lack of understanding on the characteristics of storm surges in Vietnam. Physical processes that influence the non-tidal water level associated with tropical storms can persist for up to 14 days, beginning 3–4 days prior to storm landfall and cease up to 10 days after the landfall of the typhoon. This includes the forerunner, ‘direct’ storm surge, and coastally trapped waves. This study used a continuous record of six sea level time series collected over a 5-year period (2013–2017) from along the Vietnam coast and Hong Kong to examine the contribution of the forerunner to non-tidal water level. The forerunner is defined as the gradual increase in mean water level, 2–3 days prior to typhoon landfall and generated by shore parallel winds and currents that result in a mean higher water level at the coast. Results indicated that a forerunner was generated by almost all typhoons, at least at one station, with a range between 20 and 50 cm. The forerunner contributed up to 50% of the water level change due to the storm. Combination of forerunner and onshore winds generated storm surges that were much higher (to 70 cm). It was also found that the characteristics of the typhoon (e.g., path, speed, severity and size) significantly influenced the generation of the forerunner. It is recommended that the forerunner that is not currently well defined in predictive models should be included in storm surge forecasts.

Longshore drift produced by climate-modulated monsoons and typhoons in the South China Sea

Abstract Monsoons and typhoons impact the tropical coastal zones through their signature on winds and waves, leading to increased vulnerability – through erosion, marine submersion and flooding – of an ever growing coastal population. This study addresses wave-driven coastal impacts in the South China Sea (SCS), particularly along the Vietnam coast. Using 38 years of offshore wave fields from ERA-Interim reanalysis, we assess the seasonal and interannual variability of wave patterns, storminess, and wave-induced alongshore sediment transport (longshore drift). Results suggest a large seasonal coastal impact due to high-energy, northeasterly waves generated by winter monsoon winds. The net annual sediment transport is southward with significant interannual and decadal variations (20% standard deviation with particular years at 40% of the mean), presenting strong correlations with the El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) regime changes. The regime shift of 1998, from a warm to a cold PDO phase characterized by more La Nina events, is associated with an increase in winter wave energy and thus higher sediment transport (about 10%). The typhoon activity in the SCS is partly associated with that of the Pacific Northwest basin, but as a large semi-enclosed sea, presents local differences. It is positively correlated with La Nina in summer and with El Nino Modoki in winter. The summer correlation to ENSO phases is opposite to that of the whole Northwest Pacific due to competing local and remote mechanisms driving cyclone formation and trajectory. For the same reason, the effects of ENSO and PDO phases are opposite in the SCS: during the last cold PDO phase, typhoon frequency was reduced by 20%, with significant net impact on estimated sediment transport. The typhoon contribution to sediment transport is a 15% reinforcement of southward transport due essentially to winter activity. If winter monsoon and typhoons appear to work together on average, their low-frequency variability are out-of-phase. This is particularly clear at decadal scale, as cold PDO phases seem favorable to strong winter monsoon waves but detrimental to SCS typhoon numbers. These results confirm that regional climate variability (together with human factors affecting river sediment supply, coastal management of beach-dune systems, land subsidence, mangrove deforestation) is an essential part of coastal vulnerability that needs to be better assessed.