Now showing 1 - 10 of 47
  • 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
    The 2020 Hpakant jade mine disaster, Myanmar: A multi-sensor investigation for slope failure
    (2021)
    Lin, Nina Yunung
    ;
    ;
    Wang, Yu
    ;
    Quek, Yu Pin
    ;
    Lim, Jana
    ;
    Alcantara, Enner
    ;
    Ho, Huu Loc
    A quarry failure along the slopes of the Wai Khar open-pit jade mine in Hpakant, Myanmar has led to the deaths of at least 172 jade miners on 2 July 2020. This paper conducts a systematic investigation of the incident by integrating data from multiple sensors, including high-resolution optical imagery, Sentinel-1 synthetic aperture radar (SAR) images, unmanned aerial system (UAS) footage, SRTM and ALOS digital elevation models (DEMs), soil moisture product from multi-spectral Landsat-8 satellite and precipitation records from the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS). Optical imagery, UAS footage and DEMs allow us to build a comprehensive mapping of tailing areas and quarry scarps from 2010 and reconstruct the 2D pit geometry prior to failure. Deformation signals from multi-temporal SAR interferometry (MTInSAR), soil moisture variations and precipitation trends further allow us to identify possible failure causes. To evaluate the quality of deformation obtained from different distributed-scatterer phase estimators, we develop an empirical mapping function based on areal fraction values to facilitate the comparison of temporal coherence values that are differently formulated in each phase estimator. The comparison shows that phase linking algorithm outperforms the small baseline subset method in terms of signal recovery and phase reliability. Our investigation points out that the mining site is under aggressive mining cycles that are exacerbated by frequent, uncontrolled landslides. Seepage failure, which involves the expulsion of water from rapidly compacting tailings, may be a critical factor in the 2020 incident. Instead of extreme weather, the failure had occurred under normal to drier conditions. This means that the sliding planes were already in a critical state, which is evident from the accelerated deformation around the collapse area since the beginning of 2020. Based on these findings, we provide recommendations to improve mining site regulations and management practices for safer open-pit mining in Myanmar and probably in similar contexts outside Myanmar.
    WOS© Citations 10Scopus© Citations 12  64
  • Publication
    Open Access
    WOS© Citations 2Scopus© Citations 2  275  55
  • 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
    Open Access
    Use of a MODIS satellite-based aridity index to monitor drought conditions in the Pearl River basin from 2001 to 2021
    (2022)
    Niu, Kunlong
    ;
    Qiu, Junliang
    ;
    Cai, Shirong
    ;
    Zhang, Wenxin
    ;
    Mu, Xiaolin
    ;
    ;
    Yang, Xiankun
    In recent decades, global climate change has made natural hazards increasingly prevalent. Droughts, as a common natural hazard, have been a hot study topic for years. Most studies conducted drought monitoring in arid and semi-arid regions. In humid and sub-humid regions, due to climate change, seasonal droughts and seasonal water shortages were often observed too, but have not been well studied. This study, using a MODIS satellite-based aridity index (SbAI), investigated spatiotemporal changes in drought conditions in the subtropical Pearl River Basin. The study results indicated that the inter-annual SbAI exhibited a significant decreasing trend, illustrating a wetter trend observed in the basin in the past two decades. The decreasing trend in the SbAI was statistically significant in the dry season, but not in the monsoon season. The drought conditions displayed an insignificant expansion in the monsoon season, but exhibited statistically significant shrinking in the dry season. The Pearl River Basin has become wetter over past two decades, probably due to the results of natural impacts and human activities. The areas with increased drought conditions are more likely impacted by human activities such as water withdrawal for irrigation and industrial uses, and fast urbanization and increased impervious surfaces and resultant reduction in water storage capacity. This study provided a valuable reference for drought assessment across the Pearl River Basin.
    WOS© Citations 5Scopus© Citations 5  40  61
  • Publication
    Metadata only
    Novel landslide susceptibility mapping based on multi-criteria decision-making in Ouro Preto, Brazil
    (2023)
    Mantovani, Jose Roberto
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    Bueno, Guilherme Taitson
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    Alcantara, Enner
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    ;
    Cunha, Ana Paula
    ;
    Londe, Luciana
    ;
    Massi, Klecia Gili
    ;
    Marengo, Jose A.
    Weather-related disasters have caused widespread deaths and economic losses in developing countries, including Brazil. Frequent floods and landslides in Brazil are mostly climatic driven, often aggravated by human activities and poor environmental planning. In this paper, we aimed to map and discuss the susceptibility to landslides in the urban area of Ouro Preto, Brazil, a municipality with colonial and world heritage houses. We used data on precipitation, soil types, geology, digital elevation model (DEM), and land use and land cover (LULC) of high spatial resolution (1 m). The location of landslides in the urban perimeter was provided by the Civil Defense of Ouro Preto, and these were validated by fieldwork. A novel mathematical model based on multi-criteria decision-making (MCDA) and the Analytic Hierarchy Process (AHP) was used to map the susceptible areas to landslides. Results show that areas most affected by strong landslides were low-density vegetation (high susceptibility) and rocky outcrops (very high susceptibility). The largest areas susceptible to landslides are urban land use areas. Particularly, landslides that occurred in February 2022 in the region were related to intense soil saturation. With an average monthly rainfall of 122.60 mm, the uneven relief and edaphoclimatic characteristics had caused percolation of the surface runoff, naturally triggering landslides. This study supports mitigation efforts by local governments and decision-makers.
    WOS© Citations 6Scopus© Citations 8  46
  • Publication
    Metadata only
    Southeast Asia’s dynamic sand trade and the need for better data
    (Elsevier, 2024)
    Yuen, Kai Wan
    ;
    Das, Diganta
    ;
    Tran, Dung Duc
    ;

    Sand is a vital resource for modern structures but there is limited information on the scale of sand mining or what happens to the sand after it was mined. Here, we focus on Southeast Asia (SEA) as rising affluence and population growth has turned the region into a global sand mining hotspot. We estimated the sand extraction budget in each Southeast Asian country and quantified the volume sand that was exported and imported. In addition, the destinations in which the sand was exported to were detailed and we also clarified the origins of the imported sand. Our analysis revealed that locally mined sand was mostly consumed domestically, and sand was imported if supply was insufficient. In addition, the sand trade in SEA was also predominantly regional. Unfortunately, our understanding of the sand trade in SEA was hampered by limited and inconsistent data. For example, missing data meant that production and trade flows were unavailable for some years. The volume of sand traded between each country was also uncertain due to the mismatch of trade data. Additional information on the type of sand traded was also lacking. The reliability and credibility of existing data should be strengthened to improve material accounting.

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