Sedimentation and Survival of the Mekong Delta: A Case Study of Decreased Sediment Supply and Accelerating Rates of Relative Sea Level Rise

Nittrouer, Charles A.; Ogston, A. S.; Mullarney, Julia C.; Nguyen, Thanh Thuy

doi:10.5670/oceanog.2017.318

Cited by 48 publications

(29 citation statements)

References 51 publications

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“…Larger reduction are expected in the coming decades. Dam development in the Mekong drainage basin may potentially cause major changes in the amount of sediment transported to the delta 34 . Major dam construction began in the Mekong basin in 1993; by April 2016, 35 dams had been commissioned for hydropower, irrigation reservoirs, and drinking water supply.…”

Section: Discussionmentioning

confidence: 99%

“…Concerning anthropogenic subsidence, groundwater pumping from the deep multi-aquifer system has significantly contributed, in the range of 10 to 25 mm/yr 16 , to the present land subsidence in the VMD over the last few decades. Oil and gas activities are also on the rise offshore of the VMD with areas undergoing seismic exploration and some initial drilling by the Vietnam National Oil and Gas Group (PetroVietnam) and international partners 34 . Future hydrocarbon explorations may contribute as well to subsidence of the delta.…”

Section: Discussionmentioning

confidence: 99%

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The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam

Zoccarato

Minderhoud

Teatini

2018

Sci Rep

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The Vietnamese Mekong Delta was formed by rapid transgression during the second half of the Holocene by deposition of mainly unconsolidated, fine-grained (clayey) sediments undergoing high compaction rates. The natural subsidence can seriously impact the already vulnerable delta plain as its low elevation exposes the delta to global sea level rise, flooding, salinization. Human activities such as groundwater pumping, infrastructural loading, sand mining and dam construction have exacerbated the effects of natural consolidation. Here we present a novel modeling study that has allowed to reproduce the formation and evolution of the Mekong delta over the past 4000 years. Using an adaptive finite-element mesh, the model properly simulates accretion and natural consolidation characterizing the delta evolution. Large soil grain motion and the delayed dissipation of pore-water overpressure are accounted for. We find that natural compaction of Holocene deposits following delta evolution exceeds predicted values of absolute sea level rise. The unprecedented high rates (up to ~20 mm/yr) threaten the lower delta plain with permanent inundation and inevitably reduce the designed service life of flood defense structures along the coast. Total subsidence and sediment delivery to the delta plain will determine its future elevation and vulnerability to relative sea level rise.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam

Zoccarato

Minderhoud

Teatini

2018

Sci Rep

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“…Following the ravages of the Viet Nam War (1960)(1961)(1962)(1963)(1964)(1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972) on the delta's forests, these important advantages have significantly impacted the mangroves of the delta, notably in the muddy southwestern and Gulf of Thailand areas where large tracts have been removed to provide timber for charcoal and for the construction industry, and to make place for shrimp farms and aquaculture (Phan and Hoang, 1993;Christensen et al, 2008;Veettil et al, 2019). Several recent studies have also shown that erosion is becoming increasingly rampant along much of the delta shoreline (Anthony et al, 2015;Besset et al, 2016;Allison et al, 2017;Li et al, 2017), leading to the recurrent displacement of coastal populations (Boateng, 2012) and increasing recourse to coastal protection structures, notably dykes (Albers and Schmitt, 2015). Sea dykes are being increasingly built along parts of the muddy East Sea and Gulf of Thailand coasts for protection from marine flooding and for shrimp farms, generating a process of 'mangrove squeeze' (Phan et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Mangroves and shoreline erosion in the Mekong River delta, Viet Nam

Besset

Gratiot²,

Anthony³

et al. 2019

Estuarine, Coastal and Shelf Science

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The question of the rampant erosion of the shorelines rimming the Mekong River delta has assumed increasing importance over the last few years. Among issues pertinent to this question is how it is related to mangroves. Using high-resolution satellite images, we compared the width of the mangrove belt fringing the shoreline in 2012 to shoreline change (advance, retreat) between 2003 and 2012 for 3687 crossshore transects, spaced 100 m apart, and thus covering nearly 370 km of delta shoreline bearing mangroves. The results show no significant relationships. We infer from this that, once erosion sets in following sustained deficient mud supply to the coast, the rate of shoreline change is independent of the width of the mangrove belt. Numerous studies have shown that: (1) mangroves promote coastal accretion where fine-grained sediment supply is adequate, (2) a large and healthy belt of fringing mangroves can efficiently protect a shoreline by inducing more efficient dissipation of wave energy than a narrower fringe, and (3) mangrove removal contributes to the aggravation of ongoing shoreline erosion. We fully concur, but draw attention to the fact that mangroves cannot accomplish their land-building and coastal protection roles under conditions of a failing sediment supply and prevailing erosion. Ignoring these overarching conditions implies that high expectations from mangroves in protecting and/or stabilizing the Mekong delta shoreline, and eroding shorelines elsewhere, will meet with disappointment. Among these false expectations are: (1) a large and healthy mangrove fringe is sufficient to stabilize the (eroding) shoreline, (2) a reduction in the width of a large mangrove fringe to the benefit of other activities, such as shrimpfarming, is not deleterious to the shoreline position, and (3) the effects of human-induced reductions in sediment supply to the coast can be offset by a large belt of fringing mangroves. Highlights ► We compared Mekong delta shoreline change between 2003 and 2012 and width of fringing mangroves. ► We found no significant relationships between the rate of shoreline change and mangrove width. ► Large tracts of the delta shoreline are eroding due to inadequate mud supply. ► When mud supply replenishment is low, even a wide mangrove belt will retreat. ► Mangrove protection initiatives need to consider sustained sediment supply as a key parameter.

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“…As the Mekong River approaches Vietnam's East Sea (South China Sea), the river channel becomes less steep, the river waters lose their carrying capacity, and sediments are deposited to form the Mekong Delta. Over geological time, much of the land that is now southern Vietnam was created in this manner, although present land-building processes may be changing due to dam construction, sediment mining, removal of marshes, construction of dikes, and sea level rise (Allison et al, 2017, andLiu et al, 2017, both in this issue).…”

Section: Introductionmentioning

confidence: 99%

A Question of Scale: How Turbulence Around Aerial Roots Shapes the Seabed Morphology in Mangrove Forests of the Mekong Delta

Mullarney¹,

Henderson²,

Norris³

et al. 2017

Oceanog.

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Sedimentation and Survival of the Mekong Delta: A Case Study of Decreased Sediment Supply and Accelerating Rates of Relative Sea Level Rise

Cited by 48 publications

References 51 publications

The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam

The role of sedimentation and natural compaction in a prograding delta: insights from the mega Mekong delta, Vietnam

Mangroves and shoreline erosion in the Mekong River delta, Viet Nam

A Question of Scale: How Turbulence Around Aerial Roots Shapes the Seabed Morphology in Mangrove Forests of the Mekong Delta

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