Science & Technology Development Journal - Science of The Earth & Environment

Study of flow in Rua island on Dong Nai river using 3D numerical method

2022-01-31T22:20:15+00:00

Erosion and bank erosion are processes occurring to the riverbed and are issues closely related to the people and society. Rua Island is located in Thanh Hoi commune, Tan Uyen town, Binh Duong province which is one of serious bank erosion areas in the downstream of the Dong Nai river. Riverbank erosion in Rua islet in general has been going on for a long time and the rate of bank erosion has increased after the Tri An hydropower project came into operation and river-bed sand mining activities accelerated. At present, the Rua Islet is in danger of being cut in two at the position of Rua neck. Therefore, researching to determine the mechanism and cause of landslide of Rua Islet in order to point out effective measures to prevent landslide is urgent. A three-dimensional numerical modeling has been developed for the river section in this island to study the flow structure. This model was calibrated with observation data in 2017. Using this model flow in the entire river section was simulated. The calculation results clearly showed the three-dimensional structure of the flow at this river section, especially at the curved sections where bank erosion often occurs. Calculation results also show the distribution of bottom stresse in the river section, it is a parameter that is crucial to the process of changing of the river bed.

Integrating Fuzzy-AHP and Fuzzy-GIS method in zoning wind power development in Bac Lieu province towards sustainability

2022-02-12T22:52:15+00:00

From the perspective of economic, environmental, and social point of view , Wind project site selection is a difficult problem with many criteria to consider. In this study, a proposed decision support tool was developed by the integration of the Fuzzy Analytical Hierarchy Process Method (Fuzzy-AHP) and Fuzzy Geographic Information System (Fuzzy–GIS) methods. Fuzzy-AHP was used to determine the weights of the criteria and the Fuzzy-GIS was used to normalize the data and develop the maps for optimal option determination. The study has proposed two sets of evaluation criteria, including a set of exclusion criteria and a set of criteria for ranking priority of wind power plant locations. The set of evaluation criteria was divided into 3 criteria and 10 sub-criteria. Besides, the research results showing the suitability with the wind power development planning in Bac Lieu province, an outstanding result of the study is: While local decision-makers considered that the rice fields, which account for 83.86% of the total area of the province, were unsuitable for wind power development, we found that the rice fields should be included in the planning consideration area because of the high wind speed as well as the positive effects of wind farms on crop yields and minimizing negative impacts on the natural environment.

Assessment of the status of techniques to attract farming swiftlets (Aerodramus fuciphagus amechanus) and noise impacts of the speaker intension of swiftlet farming houses in key area in Ho Chi Minh City

2022-04-24T21:06:52+00:00

This paper presents the results of assessing the status of techniques to attract swiftlets, technology to operate swiftlet houses by PRA method combined with direct survey of swiftlet houses in key areas in Ho Chi Minh City. The results show that the number of swiftlet houses is concentrated mainly in Can Gio district with 481 swiftlet houses, method of attracting swiftlets in which the combination of sound and feces accounts for the highest proportion of the methods with 37.14%. The most used sound is the sound of flock of swiftlets, which is used outside with 74.29%, the cry of a baby bird (lullaby) is used the most inside with 74.29%. The number of households that play the loudspeakers daily inside is 94.29% and the playing time is 19.84 hours. While the external speaker is 91.43% and the playing time is 12.17 hours, the sound system originates from Vietnam and Malaysia. Most of the swiftlet houses have a temperature measurement system (82.86%) and most are automatic (77.14%). The assessment of the noise level from the loudspeaker for the swiftlet house by a hand-held noise meter SL4202 that measures the noise according to Vietnamese Standard TCVN 7878-1:2008 shows that the average noise level in the swiftlet house area in Can Gio and Long Phuoc commune, district 9 is 1.1 and 1.4 DBA higher than QCVN 26, respectively.

Land-cover classification using Random Forest and incorporating NDVI time-series and topography: a case study of Thanh Hoa province, Vietnam

2022-05-02T22:36:58+00:00

Land cover/land use (LULC) mapping in the complex land cover area is a challenging task due to the mixed vegetation patterns, and rough mountains with fast-flowing rivers. Therefore, a new technique should be applied to improve the accurate classification of complex LULC. In this study, we applied a supervised machine learning approach to map land use in Thanh Hoa province, Vietnam utilizing multi-temporal Normalized Difference Vegetation Index (NDVI) data from MODIS, combined with topographic features. We used distinctive temporal features of land cover in 2015 as response variables and developed fifteen engineering features as predictors for automatic prediction. Then, we trained Random Forest classification (RFC) and conducted repeated cross-validation to identify the optimal RFC with the highest robustness on test data. RFC reached a total prediction accuracy of 91 % and Kappa coefficient (K) of 0.89 across eight different land covers including bareland, crops, rice paddy, forest, mangrove, urban and built up, grassland, and water. Besides, the results showed that the features extracted from time-series NDVI comprising the mean of yearly NDVI, the sum of NDVI, and the topography were the relative importance variables controlling the land cover classification.

Assessment of water quality changes in Saigon and Dong Nai rivers under the influence of domestic wastewater discharges

2022-05-03T21:40:24+00:00

The study was conducted to evaluate the impact of domestic wastewater discharges on surface water quality (BOD5 and DO) at pumping stations on Sai Gon – Dong Nai river during the dry season and the wet season using the MIKE 21FM model. The results indicated that the water quality in Dong Nai river is rated better than the Sai Gon River. Specifically, the BOD5 concentration was high, and the DO concentration was low at Hoa Phu station in Sai Gon River. However, the surface water quality at pumping stations on Dong Nai river, namely Hoa An and Binh An was up to standard compared to column A2 for domestic water supply purposes according to QCVN 08- MT:2015/BTNMT. Specifically, the wastewater source from Thu Dau Mot city on the Sai Gon river was about 4 km from Hoa Phu pumping station with a discharge volume of 0,66 m3/s, and another source from Bien Hoa city on the Dong Nai river reached a discharge volume of 2,15 m3/s, which was about 4.7 km and 5.5 km from Hoa An and Binh An intakes, respectively. The outcomes proved that Hoa Phu and Hoa An pumping stations were not affected by the wastewater from these cities. Otherwise, there was markedly degraded water quality at Binh An intake in the dry season, which was unsatisfied with QCVN 08- MT:2015/BTNMT (A2 type).

Application of Attribute Recognition model to assess sustainability in land use in Tay Ninh province

2022-05-03T21:58:30+00:00

The purpose of the article is to apply the model of identifying attributes to assess the sustainability of 4 main types of arable land use in Tay Ninh province on the basis of selecting indicators, updating data and applying statistical principles. to divide the sustainability level, use the formulas of the ARM model to calculate the hierarchy of sustainability for each facet and for aggregate stability. The economic results show that sugarcane is the most sustainable type of farming with absolute probability 1.0 and the least sustainable type is tapioca with probability 0.5. Socially, rubber, tapioca and sugarcane are most clearly shown at the very stable level with probability 0.4, respectively; 0.48 and 0.42; In terms of resources and environment, most of the four types of land use are shown at the weak and medium levels of sustainability. As a result of the combined sustainability in all three aspects of economic, social and environmental resources, sugarcane is a crop that is clearly shown at the very sustainable level, rice - color is shown at the fairly sustainable level, rubber and medium sustainable cassava. The indicators of unsustainability need to be improved according to the roadmap, in addition to the indicators that need to be maintained at a fairly sustainable level, and also pointed out 6 unsustainable causes as the main relevant factors. books, markets, science and technology, economics, society and the environment. The research results of the article will be an important scientific basis in the management and use of agricultural land in Tay Ninh province in particular and other localities in the country in general.

Developing a set of indicators to assess sustainability in land use in Tay Ninh province

2022-05-16T20:39:03+00:00

This paper presents a study aimed at developing a set of indicators to assess the sustainability of agricultural land use applicable in Tay Ninh province. The set of directives is built based on FAO's principles of sustainable agricultural land use combined with expert knowledge, suitable to the natural - economic - social conditions of Tay Ninh province. Research and apply the AHP method to screen indicators, overcome the subjectivity and arbitrariness in choosing each indicator to participate in the assessment. The result of building a set of indicators includes 13 indicators, of which economic sector 3 indicators, social sector 5 indicators, natural resources and environment 5 indicators. Based on practical conditions, Tay Ninh province selects 4 main types of arable land use corresponding to each land unit, updates the data for the indicator set, and applies data normalization techniques by ratio. the difference brings all data to the same value, conducting a preliminary comparison of the efficiency of land use types. The development of a set of indicators can help localities have more tools and measurement methods in applying the assessment of sustainability in agricultural land use in particular and contribute to further scientific research. sustainable development in general.

A review on the role of the Mekong River in contributing terrigenous sediments in the southwest East Sea

2022-03-03T20:51:48+00:00

The Mekong River is the largest river surrounding the East Sea and transports much terrigenous sediments to the southwestern East Sea. However, this region still has contained different standpoints on the sediment contribution from the Mekong River. In this study, clay mineralogy and elemental geochemistry of cores MD01-2393, MD97-2150, SO18383-3, 86GC, and KC09 from previous studies are employed to review sediment provenances in the southwestern East Sea and the role of the Mekong River in contributing terrigenous sediments in this region. According to clay mineralogy and elemental geochemistry, provenance analyses indicate that the Mekong River primarily provides terrigenous sediments to the southwestern East Sea, while rivers in Borneo, Malay, Sumatra, and Thailand can supply insignificant amounts of terrigenous sediments to this area. Based on the abundance of fine grain (silt and clay) and foraminifera in sediment cores, terrigenous sediments in the southwestern East Sea cannot be weathering products of parent rocks in the deep-sea basin, implying that these sediments could originate from remote sources. Our study reveals that the Mekong River plays the most crucial role in contributing terrigenous sediments to the southwestern East Sea.