The Vietnamese Mekong Delta(VMD),a critical agricultural hub,faces recurrent flooding that poses substantial threats to livelihoods and productivity.Ben Tre province,with its low-lying coastal terrain,is particularly ...The Vietnamese Mekong Delta(VMD),a critical agricultural hub,faces recurrent flooding that poses substantial threats to livelihoods and productivity.Ben Tre province,with its low-lying coastal terrain,is particularly vulnerable.Effective risk management and sustainable agricultural development necessitate a thorough understanding of these flood dynamics.This study leveraged the Google Earth Engine(GEE)platform and Sentinel-1 Synthetic Aperture Radar(SAR)imagery to analyze flood inundation patterns and their impacts on diverse agricultural land uses in Ben Tre province from 2015 to 2023.The methodology involved SAR data pre-processing,Otsu thresholding for water body delineation from VH polarization data and change detection using a 2020 land use map to quantify annual flooded areas and their impact on specific agricultural categories.The total inundated area peaked in 2018 at 58,334 ha,a significant increase from 27,934 ha in 2015,before stabilizing around 42,000–44,000 ha in 2021–2023.Flooded agricultural land mirrored this trend,increasing from 18,615 ha(2015)to a peak of 39,514 ha(2018),then decreasing to 28,841 ha(2023).Notably,wet rice cultivation experienced a 37.8%increase in its flooded area over the study period,while other annual crops and perennial crops saw increases of 38.9% and 68.4%,respectively.This research demonstrates the GEE platform’s efficacy with Sentinel-1 SAR for robust,long-term flood monitoring and impact assessment,revealing escalating flood pressure on key agricultural systems and an expansion of flooding beyond traditional low-lying zones,providing crucial data for adaptive land use planning.展开更多
In recent years,the water level in the Mekong Delta(MD)has undergone changes,attributed to the impacts of anthropogenic activities and climate change.Declining water levels have had implications for various aspects of...In recent years,the water level in the Mekong Delta(MD)has undergone changes,attributed to the impacts of anthropogenic activities and climate change.Declining water levels have had implications for various aspects of life and aquatic ecosystems in the lower basin water bodies.Analyzing long-term trends in rainfall and water levels is crucial for enhancing our understanding.This study aims to examine the evolving patterns of water level and rainfall in the region.Data on water levels and rainfall from observation stations were gathered from the National Center for Hydrometeorological Forecasting,Vietnam,spanning from 2000 to 2014.The assessment of homogeneity and identification of trend changes were conducted using the Standard Normal Homogeneity Test(SNHT)and the Mann-Kendall test.The results indicate that changes in water levels at the Tan Chau and Chau Doc stations have been observed since 2010 due to the operation of flow-regulating structures in the upper Mekong River.Following the commencement of upstream dam operations,the water level at the headwater stations of the Mekong River has been higher than the long-term average during the dry season and lower than the average during the flood season.The study findings highlight the influence of altered rainfall patterns under the impact of climate variability(ICC)on water level trends in the study area.While rainfall plays a significant role in increasing water levels during the flood season,the operation of hydropower dams(UHDs)stands out as the primary factor driving water level reductions in the study area.展开更多
The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta(VMD)plays an important role in Vietnam’s agricultural and aquaculture production activities.However,recent variations ...The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta(VMD)plays an important role in Vietnam’s agricultural and aquaculture production activities.However,recent variations in water levels and flow patterns,driven by both human activities and climate change(CC),have posed significant challenges for water resource management.This study evaluates the impacts of unsustainable exploitation and CC on the hydrological regime of the Tien and Hau Rivers using non-parametric statistical methods.Long-term water level data(1978–2023)from Tan Chau,Chau Doc,and Vam Nao observation stations were analyzed using the Mann-Kendall test(MK),Sen’s Slope(SS)estimator,and Pettitt’s test to detect trends,quantify change magnitudes,and identify abrupt shifts.The results indicate a significant decline in flood-season water levels,with annual decrease rates ranging from 41.5 to 72.9 mm in September and November.Conversely,a slight increasing trend in water levels was observed in the dry season(DS)during the studied time.Additionally,findings reveal that the upstream Tien River exerts greater control over the hydrological regime in the Vam Nao River.These insights contribute to disaster risk assessment,sustainable water resource planning,and ecological risk evaluation.Furthermore,the results contribute to providing a foundation for applying hydrological and hydraulic models to forecast hydrodynamics,thereby supporting effective water management strategies and mitigating flood and dry risks in the VMD.展开更多
Rip currents are a significant threat to swimmers worldwide,responsible for numerous drowning incidents each year.In Vietnam,Bai Dai Beach in Cam Ranh Bay,Khanh Hoa Province,has experienced an increase in drowning eve...Rip currents are a significant threat to swimmers worldwide,responsible for numerous drowning incidents each year.In Vietnam,Bai Dai Beach in Cam Ranh Bay,Khanh Hoa Province,has experienced an increase in drowning events due to rip currents in recent years.To address this issue,a comprehensive study was conducted based on developing a depth-averaged 2D hydrodynamic model to simulate rip currents in the Bai Dai-Cam Ranh coast.The HYDIST-2D numerical model was applied to simulate the rip current evolution in space and time for the study area.The results showed that the HYDIST-2D numerical model can accurately predict the location,magnitude,and microstructure of rip currents,including rip current speed,width,and length.The simulation results revealed that the rip current speed is greater during the low tide phase,with an average speed of 0.5 m s^(-1),while during high tide,the rip current speed is lower,around 0.1–0.8 m s^(-1).The width and length of the rip current also vary with the tide phase,with a wider and longer rip current observed during the low tide phase.The results also showed that the rip current speed and microstructure are influenced by the wave features,tide current,and bathymetry of the study area.The present study provides valuable insights into the dynamics of rip currents in the Bai Dai-Cam Ranh coast.The findings can be used to support the management of bathing activities and provide early warnings for potential risks associated with rip currents.展开更多
基金funded by the University of Science,VNU-HCM under grant number T2023-107.
文摘The Vietnamese Mekong Delta(VMD),a critical agricultural hub,faces recurrent flooding that poses substantial threats to livelihoods and productivity.Ben Tre province,with its low-lying coastal terrain,is particularly vulnerable.Effective risk management and sustainable agricultural development necessitate a thorough understanding of these flood dynamics.This study leveraged the Google Earth Engine(GEE)platform and Sentinel-1 Synthetic Aperture Radar(SAR)imagery to analyze flood inundation patterns and their impacts on diverse agricultural land uses in Ben Tre province from 2015 to 2023.The methodology involved SAR data pre-processing,Otsu thresholding for water body delineation from VH polarization data and change detection using a 2020 land use map to quantify annual flooded areas and their impact on specific agricultural categories.The total inundated area peaked in 2018 at 58,334 ha,a significant increase from 27,934 ha in 2015,before stabilizing around 42,000–44,000 ha in 2021–2023.Flooded agricultural land mirrored this trend,increasing from 18,615 ha(2015)to a peak of 39,514 ha(2018),then decreasing to 28,841 ha(2023).Notably,wet rice cultivation experienced a 37.8%increase in its flooded area over the study period,while other annual crops and perennial crops saw increases of 38.9% and 68.4%,respectively.This research demonstrates the GEE platform’s efficacy with Sentinel-1 SAR for robust,long-term flood monitoring and impact assessment,revealing escalating flood pressure on key agricultural systems and an expansion of flooding beyond traditional low-lying zones,providing crucial data for adaptive land use planning.
基金funded by the University of Science,VNU-HCM under grant number T2022-10 project entitled“Water level variability in the Mekong Delta under the impacts of anthropogenic and climatic factors”.
文摘In recent years,the water level in the Mekong Delta(MD)has undergone changes,attributed to the impacts of anthropogenic activities and climate change.Declining water levels have had implications for various aspects of life and aquatic ecosystems in the lower basin water bodies.Analyzing long-term trends in rainfall and water levels is crucial for enhancing our understanding.This study aims to examine the evolving patterns of water level and rainfall in the region.Data on water levels and rainfall from observation stations were gathered from the National Center for Hydrometeorological Forecasting,Vietnam,spanning from 2000 to 2014.The assessment of homogeneity and identification of trend changes were conducted using the Standard Normal Homogeneity Test(SNHT)and the Mann-Kendall test.The results indicate that changes in water levels at the Tan Chau and Chau Doc stations have been observed since 2010 due to the operation of flow-regulating structures in the upper Mekong River.Following the commencement of upstream dam operations,the water level at the headwater stations of the Mekong River has been higher than the long-term average during the dry season and lower than the average during the flood season.The study findings highlight the influence of altered rainfall patterns under the impact of climate variability(ICC)on water level trends in the study area.While rainfall plays a significant role in increasing water levels during the flood season,the operation of hydropower dams(UHDs)stands out as the primary factor driving water level reductions in the study area.
文摘The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta(VMD)plays an important role in Vietnam’s agricultural and aquaculture production activities.However,recent variations in water levels and flow patterns,driven by both human activities and climate change(CC),have posed significant challenges for water resource management.This study evaluates the impacts of unsustainable exploitation and CC on the hydrological regime of the Tien and Hau Rivers using non-parametric statistical methods.Long-term water level data(1978–2023)from Tan Chau,Chau Doc,and Vam Nao observation stations were analyzed using the Mann-Kendall test(MK),Sen’s Slope(SS)estimator,and Pettitt’s test to detect trends,quantify change magnitudes,and identify abrupt shifts.The results indicate a significant decline in flood-season water levels,with annual decrease rates ranging from 41.5 to 72.9 mm in September and November.Conversely,a slight increasing trend in water levels was observed in the dry season(DS)during the studied time.Additionally,findings reveal that the upstream Tien River exerts greater control over the hydrological regime in the Vam Nao River.These insights contribute to disaster risk assessment,sustainable water resource planning,and ecological risk evaluation.Furthermore,the results contribute to providing a foundation for applying hydrological and hydraulic models to forecast hydrodynamics,thereby supporting effective water management strategies and mitigating flood and dry risks in the VMD.
文摘Rip currents are a significant threat to swimmers worldwide,responsible for numerous drowning incidents each year.In Vietnam,Bai Dai Beach in Cam Ranh Bay,Khanh Hoa Province,has experienced an increase in drowning events due to rip currents in recent years.To address this issue,a comprehensive study was conducted based on developing a depth-averaged 2D hydrodynamic model to simulate rip currents in the Bai Dai-Cam Ranh coast.The HYDIST-2D numerical model was applied to simulate the rip current evolution in space and time for the study area.The results showed that the HYDIST-2D numerical model can accurately predict the location,magnitude,and microstructure of rip currents,including rip current speed,width,and length.The simulation results revealed that the rip current speed is greater during the low tide phase,with an average speed of 0.5 m s^(-1),while during high tide,the rip current speed is lower,around 0.1–0.8 m s^(-1).The width and length of the rip current also vary with the tide phase,with a wider and longer rip current observed during the low tide phase.The results also showed that the rip current speed and microstructure are influenced by the wave features,tide current,and bathymetry of the study area.The present study provides valuable insights into the dynamics of rip currents in the Bai Dai-Cam Ranh coast.The findings can be used to support the management of bathing activities and provide early warnings for potential risks associated with rip currents.
