River bank instability from unsustainable sand mining in the lower Mekong River

Hackney, Christopher; Darby, Stephen E.; Parsons, Daniel R.; Leyland, Julian; Best, James L.; Aalto, R. E.; Nicholas, A. P.; Houseago, Robert C.

doi:10.1038/s41893-019-0455-3

Cited by 216 publications

(185 citation statements)

References 39 publications

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“…In this context, from a reductionist point of view, single bifurcations of the delta represent the building blocks, controlling the distribution of water, sediment, and nutrient fluxes among the branches. Understanding their dynamics is therefore important in an era of climate changes and anthropogenic pressure on coastal areas that makes deltas vulnerable elements, threatened by degradation due to extraction of natural resources (oil and gases, and sand mining), land reclamation, sediment retention by reservoirs, and harbors development (Hackney et al, 2020;Hoitink et al, 2017Hoitink et al, , 2020.…”

Section: Introductionmentioning

confidence: 99%

Effect of Small Tidal Fluctuations on the Stability and Equilibrium Configurations of Bifurcations

2020

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Deltas are fascinating landforms subject to fluvial and marine forcing. Bifurcations are common features in deltas, governing the distribution of water and sediment fluxes among the distributary channel network. Recently, it has been observed that tide‐influenced deltas tend to display less numerous but more stable branches in comparison to their riverine counterparts. River bifurcations subject to unidirectional flow have been widely studied in the last decades. In contrast, the acting physical mechanisms and factors controlling the stability of bifurcations in tide‐influenced deltas are still not well understood, and a theoretical framework is still lacking. In order to fill this gap and understand how the stability and evolution of bifurcations in distributary deltaic systems could be affected by the tides, we investigate, through an analytical model, the equilibrium configurations and stability of tidal bifurcations under the hypothesis of small monochromatic tidal oscillations. In particular, we build on previous works on river bifurcations, incorporating the solution for the equilibrium of a single‐river‐dominated estuary. We find that higher tidal amplitudes and a closer proximity of the junction node to the sea tend to hamper the development of unbalanced solutions, reducing the asymmetries in water and sediment fluxes between branches. This stabilizing effect exerted by the tidal action is associated with the erosive character of the tidal currents that promotes channel deepening and increases the capacity of the system to keep morphodynamically active both bifurcates in comparison with the purely fluvial case. Preliminary field observations of natural deltas corroborate our findings.

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Section: Introductionmentioning

confidence: 99%

Effect of Small Tidal Fluctuations on the Stability and Equilibrium Configurations of Bifurcations

2020

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“…Delta subsidence, driven by compaction of sedimentary strata 13 , is also being accelerated due to increased rates of ground water extraction 14,15 . Furthermore, many large deltas are also sediment starved 16 due to major reductions in the supply of fluvial sediment caused by upstream dam construction 17,18 , rapid and accelerating sand mining 19,20 , and the construction of flood embankments 12,21,22 . Such sediment starvation potentially compromises the ability of deltas to offset rising sea-levels through sediment deposition 1,23 .…”

Section: Here We Use New Field Data and Hydrodynamic Modelling To Quamentioning

confidence: 99%

“…These declining rates of fluvial sediment supply have been attributed to the effects of shifting tropical cyclonic tracks 31 as well as extensive river impoundment and hydropower development across the Mekong's catchment 18 . Furthermore, sections of the river and its delta have been subject to intensive sand mining, some of which is not regulated 32 , with official statistics alone documenting annual removal rates in excess of 50 Mt yr -1 (33) compared to sand influx rates of 6.2±2.0 Mt yr -1 at the delta apex 20 . As a result, similar to other large deltas such as the Chao Phraya 34,35 , Pearl 36 , Yangtze 37 and Yellow 38 , the Mekong is subject to severe, anthropogenically-driven, sediment starvation, resulting in rapid and extensive channel erosion 39 .…”

Section: Here We Use New Field Data and Hydrodynamic Modelling To Quamentioning

confidence: 99%

Anthropogenic sediment starvation forces tidal dominance in a mega-delta

Vasilopoulos¹,

Quan²,

Parsons³

et al. 2020

Preprint

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The world’s major river deltas provide bountiful ecosystem services to hundreds of millions of people1,2, but there are widespread concerns that their ability to support these critical functions is being threatened by increases in salinity and the extent of tidal zones3, forced by sea-level rise4. Changes in the position of the fluvial-marine interface are governed not only by climate-driven sea-level rise, but by other factors including variations in river discharge and channel geometry5,6. However, the relative contributions of different driving factors to shifting tidal extent remains unconstrained. Here we use new field data and hydrodynamic modelling to quantify the influence of these different driving factors on accelerating tidal extension in the Mekong delta, both for the recent past and projected into the future under a range of policy, regulation and climate change scenarios. Our results indicate that, within the next two decades, tidal extension into the delta will increase by up to 56 km due to channel deepening, primarily driven by anthropogenic sediment starvation, which accounts for almost all (92%) of this incursion. Eustatically rising sea-levels are found to contribute only modestly. These findings will be transferable to other large sediment starved deltas that are facing similar challenges.

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“…Current condition estimated that the volume of extracted sand is around 2544.96 m³/day or 890736 m³/year. The volume will continue to grow in line with the need for sand as construction material (Hackney et al, 2020). UNEP report of 2014 estimated that sand and gravel are extracted each year globally with demand increasing, especially in developing countries (Bravard et al, 2013;Schandl et al, 2016;Prasad et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Impact of sand mining on the changes of morphological and physical dynamics in Sa’dang River, Pinrang District, Indonesia

Arsyad

Rukmana

Salman

et al. 2020

J.Degrade.Min.Land Manage.

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The research aimed to investigate the morphological changes and physical dynamics conditions of the Sa'dang River associated with river sand mining activities. The research is expected to benefit the efforts of the management of sand mining in this area and enrich knowledge about the issues of river sand mining. The study was conducted in Sa'dang River sand mining area, which includes villages of Pincara, Massewwae and Mangki of Pinrang District in South Sulawesi Province, Indonesia. A field survey was conducted in October to December 2019 to see the condition of the river along with the mining activities that were taking place. Field data analysis was combined with google earth imagery data for 2006, 2014, 2017 and 2019 using ArcGIS 10.5 software to see changes in river morphology, formation and extent of point bar and channel bar, as well as changes in the area of river water bodies and non-water river bodies. The results showed that the changes in morphology and physical dynamics conditions of the Sa'dang River showed their own pattern. If sediment deposits forming point bars or channel bars were reduced, the area of river water bodies tended to increase. Or in other words, the width of the river is inversely proportional to the increase in the area of the river water body if the area of sediment deposits that form the point bar and channel bar tends to decrease.

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River bank instability from unsustainable sand mining in the lower Mekong River

Cited by 216 publications

References 39 publications

Effect of Small Tidal Fluctuations on the Stability and Equilibrium Configurations of Bifurcations

Effect of Small Tidal Fluctuations on the Stability and Equilibrium Configurations of Bifurcations

Anthropogenic sediment starvation forces tidal dominance in a mega-delta

Impact of sand mining on the changes of morphological and physical dynamics in Sa’dang River, Pinrang District, Indonesia

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