Now showing 1 - 5 of 5
  • Publication
    Open Access
    The worst 2020 saline water intrusion disaster of the past century in the Mekong Delta: Impacts, causes, and management implications
    (2021) ;
    Ho, Huu Loc
    ;
    Doan, Van Binh
    ;
    Sameh Kantosh
    Vietnam Mekong Delta (VMD), the country's most important food basket, is constantly threatened by drought-infused salinity intrusion (SI). The SI disaster of 2020 is recognized as the worst in recent decades, hence inspiring this perspective article. The authors' viewpoints on the disaster's impacts and causes are presented. The arguments presented are mainly drawn from (i) up-to-date publications that report on the recent SI intensification in the VMD and (ii) the power spectral analysis results using water level data. We verified the intensifying SI in the VMD both in its frequency and magnitude and remarked on four of the key SI drivers: (i) upstream hydropower dams, (ii) land subsidence, (iii) the relative sea-level rise, and (iv) riverbed sand mining. Also, a non-exhaustive yet list of recommendable management implications to mitigate the negative effects of the SI is contributed. The mitigation measures must be realized at multiple scales, ranging from pursuing transboundary water diplomacy efforts to managing internal pressures via developing early warnings, restricting illegal sand mining activities, alleviating pressures on groundwater resources, and diversifying agriculture.
    WOS© Citations 39Scopus© Citations 39  74  303
  • Publication
    Metadata only
    New systematically measured sand mining budget for the Mekong delta reveals rising trends and significant volume underestimations
    (2022)
    Gruel, Charles-Robin
    ;
    ;
    Switzer, Adam D.
    ;
    Sonu, Kumar
    ;
    Ho, Huu Loc
    ;
    Sameh, Kantoush
    ;
    Doan, Van Binh
    ;
    Feng, Lian
    The river beds of the Mekong Delta are some of the most intensively sand mined places in the world. However, sand mining budgets remain limited to rough and indirect estimates. Here, we provide a first systematic, field-based estimation of the Mekong Delta’s sand mining budget. This budget overcomes the limitations of relying on officially declared statistics and bathymetric surveys of short channel reaches. We applied Sentinel-1 radar imagery to monitor the distribution of sand mining activities using boat metrics-driven mining intensity maps correlated with a field-based bathymetry difference map which were derived from two extensive bathymetric surveys conducted in 2014 and 2017. The two surveys cover ∼ 100 km in the Tiền River, reaching approximately 15% of the Mekong Delta. We then extrapolated the Tiền River findings to the broader Vietnamese Mekong Delta from 2015 to 2020 and measured a continuous increase of the extraction budget by ∼ 25% between 2015 (38 Mm3/yr) and 2020 (47 Mm3/yr). We estimated a total sand mining budget of 254 Mm3 during the 6-year study period with an average annual rate of ∼ 42 Mm3. Our field-based annual rates are higher than both official declarations provided and estimates from previous studies which implies that a substantial portion of the sand mining budget remains unaccounted for. Riverbed sand mining remains a key threat to the Mekong Delta as it contributes to a multitude of other environmental threats including dam construction effects on sedimentation, ongoing subsidence, sea level rise and recurring saltwater intrusion. This study offers a new approach that can be implemented elsewhere to allow for systematic monitoring and quantification of sand mining activities that are vital for assessing future projections on environmental impacts.
    WOS© Citations 13Scopus© Citations 15  49
  • Publication
    Metadata only
    A deep learning framework to map riverbed sand mining budgets in large tropical deltas
    (Taylor & Francis, 2023)
    Suno Kumar
    ;
    ;
    Tran, Dung Duc
    ;
    Wang, Jinyu
    ;
    Ho, Huu Loc
    ;
    Feng, Lian
    ;
    Sameh, A. Kantoush
    ;
    Van Binh, Doan
    ;
    Li, Dongfeng
    ;
    Switzer, Adam D.

    Rapid urbanization has dramatically increased the demand for river sand, leading to soaring sand extraction rates that often exceed natural replenishment in many rivers globally. However, our understanding of the geomorphic and social-ecological impacts arising from Sand Mining (SM) remains limited, primarily due to insufficient data on sand extraction rates. Conventionally, bathymetry surveys and compilation of declared amounts have been used to quantify SM budgets, but they are often costly and laborious, or result in inaccurate quantification. Here, for the first time, we developed a Remote Sensing (RS)-based Deep Learning (DL) framework to map SM activities and budgets in the Vietnamese Mekong Delta (VMD), a global SM hotspot. We trained a near real-time object detection system to identify three boat classes in Sentinel-1 imagery: Barge with Crane (BC), Sand Transport Boat (STB), and other boats. Our DL model achieved a 96.1% Mean Average Precision (mAP) across all classes and 98.4% for the BC class, used in creating an SM boat density map at an Intersection over Union (IoU) threshold of 0.50. Applying this model to Sentinel-1, 256,647 boats were detected in the VMD between 2014–2022, of which 17.4% were BC. Subsequently, the annual SM budget was estimated by correlating it with a recent riverbed incision map. Our results showed that, between 2015–2022, about 366 Mm3 of sand has been extracted across the VMD. The annual budget has progressively increased from 34.92 Mm3 in 2015 to 53.25 Mm3 in 2022 (by 52%), with an annual increment of around 2.79 Mm3. At the provincial-scale, Dong Thap, An Giang, Vinh Long, Tien Giang, and Can Tho were the locations of intensive mining, accounting for 89.20% of the total extracted volume in the VMD. Finally, our estimated budgets were validated with previous research that yielded a correlation coefficient of 0.99% (with bias of 2.65%). The automatic DL framework developed in this study to quantify SM budgets has a high potential to be applied to other deltas worldwide also facing intensive SM.

    Scopus© Citations 2  3
  • Publication
    Open Access
    How the saline water intrusion has reshaped the agricultural landscape of the Vietnamese Mekong Delta, a review
    (2021)
    Ho, Huu Loc
    ;
    Low, Mindy Lixian
    ;
    ;
    Tran, Duc Dung
    ;
    Sangam Shrestha
    ;
    Yoon, Yong-Jin
    Once a key factor behind Vietnam's successful Doi Moi (restoration) economic reforms, the rice-centered agriculture of the VMD is now confronted by the new pressure of climate change impacts, including the intensifying salinity intrusion (SI). The SI menace has partly triggered the delta-wide emergence of new adaptive livelihood models across the VMD, including the prawn rice rotational crop (PRRC) that is arguably the most prominent. Research on the SI-driving factors is rapidly increasing in numbers, yet little synthesis has been done. Likewise, several studies have investigated the economic benefits of PRRC; less emphasis has placed on environmental and societal aspects, hence the questionable sustainability. This study, therefore, contributes a composite literature review, targeting two SI-related aspects: (i) key factors driving the intensification of SI in recent years across the Mekong Delta, and (ii) current understanding of the sustainability of PRRC. Results from the first review assignment highlight the four key SI-driving factors: riverbed incision, land subsidence, upstream dams, and sea-level rise. Also remarked are the critical absence of studies addressing multiple drivers and the need for a decoupling model to quantify the relative importance of each factor to strategize the adaptive measures. For PRRC, we reveal that while economic benefits have been widely reported, potential negative impacts of this model related to environmental and social aspects are lacking. Therefore, while the lucrative prawn trade might financially benefit the farmers', the economic benefit is marred by the underlying negative environmental impacts and social inequalities, limiting overall sustainability. This study also provides a case study to notify the spatial-temporal trends of PRRC in the last three decades and evaluate the associated geographical and social factors. Kien Giang province was selected as the study site since it is the largest PRRCacross the VMD. The lessons from Kien Giang can also be applied to other transformative agricultural models in both Mekong Delta and other deltas worldwide.
    WOS© Citations 31Scopus© Citations 48  302  15
  • Publication
    Open Access
    An enhanced analytical framework of participatory GIS for ecosystem services assessment applied to a Ramsar wetland site in the Vietnam Mekong Delta
    (2021)
    Ho, Huu Loc
    ;
    ;
    Tran, Ngoc Thu
    ;
    Nguyen, Thi Hong Diep
    ;
    Nguyen, Trong Can
    Public participation geographic information systems (PPGIS), though proven valuable in ecosystem services (ES) research, is occasionally criticized for being expensive in terms of time, cost and administration efforts in case the post-hoc sophisticated spatial analytics/statistics are targeted. This study, based on the enhancement of the pre-developed PPGIS analytical framework, seeks to address these critiques by introducing an in-expensive effective data collection strategy, while substantially facilitating geo-spatial analytics. The U Minh Thuong National Park (UMTNP) in the Mekong Delta in Vietnam, a world’s renowned Ramsar site, was chosen to demonstrate the framework. The respondents participated in the participatory mapping on paper maps, using color markers to hand-draw (as polygons) their self-perceived areas associated with different categories ES. By collecting 2D data, the post-hoc spatial analyses could have utilized more meaningful statistical methods. In this study, we introduced the uses of three methods: Ordinary least squares (OLS), Geographically weighted regression (GWR) and Moran’s I to assess the spatial autocorrelation of ES across the landscape. In addition to participatory mapping, the respondents were also engaged in completing a semi-structured questionnaire, which was subsequently analyzed using principal component analysis and hierarchical cluster analysis. These two multivariate analyses serve to reveal the structured diversity of the people’s perceptions towards the importance of different ES. It was shown that Provisioning ES was the most highly regarded benefit, followed by Regulating, Supporting and Cultural. Regulating and Supporting ES, the two indirect material services share relatively similar appreciation patterns while Cultural ES was unexpectedly the least credited, a stark contrast lineagainst the government designated eco-tourism and historical functions of UMTNP. Geographically, the core areas of the national park have the most overlaps between Provisioning and Regulating services. Supporting services, on the other hand, were the most associated with Provisioning and Regulating services in peripheral areas. Cultural services were synergized with the other three types of ES in the areas reserved for eco-tourism activities. The revealed spatial synergies can determine the areas where potential conflicts between extractive and non-extractive uses could occur, contributing insights for sustainable management of UMTNP and other protected areas worldwide. In addition, this study also contributes to promoting the PPGIS method in ES research and other human geographical studies, those relying on community participation.
    WOS© Citations 21Scopus© Citations 26  114  195