Assess the impacts of river sand extraction

to bank erosion at Co Chien River, Vinh

Long ProvinceNgo Thanh Hau1), Huynh Trung Tin1), Trinh Cong Luan2), Bui Trong Vinh1)

1) Faculty of Geology & Petroleum Engineering – HCMUT, Vietnam2) Mientay Construction University, Vinh Long Province, Vietnam

E-mail: haungothanh@gmail.com

December 2013

Introduction

Methods

Discussion

Conclusion

Study areaEast sea

(Vietnam sea)

Introduction

Tien river

Hau river

85km

Method

Analysis the composition of bank material

Assessment the wave impacts

River sand activity

Figure: Taking cored soil sample

Loam and sandy of alluvial Quaternary (aQ23)

Results show that, these soft soils can easily be destroyed by any

external forces

Figure: Wind wave and wave by boat (Bui Trong Vinh, 2009)

Wave by boat

Wave impact

Bed-river sand mining provides volume of construction materials that without affect to agricultural land

Advantage:

Help to dredge to navigations

Train river

Disadvantage:

Main cause to bank erosion seriously

Affect the natural habitat and environment

River sand activity

Sand mining Sensitive area

Coordinate East NorthUTM – WGS 84 (48P)

601928 1136304602865 1136125604123 1135090604723 1134480

Coordinate East NorthUTM – WGS 84 (48P)

607805 1134885608676 1134704609565 1134923610309 1134565

Method

Using the numerical modeling MIKE 21C (DHI) to evaluate

the river bank erosion impacts from excavation of sand

The results obtained from testing were extracted by cross-

section form

Field surveyMeasure

The cumulative width (m)

Left bank Right bankCross – section VI - VI

Condition 1

•Number of facilities: 1 vessel/mine

•Capacity per vessel: 0.7m3

•Velocity: 0.14m3/min

•Operated time: 10 h/day

=> Total removed sand: 153,300 m3/yr

Modelling

SECTION IV - IVRight bankLeft bank

Left bank Right bankSECTION V - V

Initial modeling

Modeling condition 1

Elev

atio

n (m

)

The cumulative width (m)

Condition 2

•Number of facility: 3 vessels/mine

•Capacity per vessel: 0.7m3

•Velocity: 0.14m3/min

•Operated time: 10 h/day

=> Total removed sand: 459,900m3/yr

Modelling

Condition 1

Condition 2

Cumulative width (m)

Elev

atio

n (m

)

By field survey results, a number of facilities were used for sand

extraction was twice to three times as many as its affordable

which operated continuously from 12 to 14 hour per day. That

had led to increasing of quantity of extraction, changing the flow

direction and creating the local bed scours which cause of

imbalance in sand replenishment rate and serious erosion.

Discussion

River sand mining activities caused bed river change and flow change.

The overmining activities of river sand mining can directly impacted to flow direction, disturbed the bottom sediment, and damaged the balance of sediment transport of the river.

Conclusion

• Bui Trong Vinh, Ichiro Deguchi, Keiji Nakatsuji, (2008).“Beach Erosion Caused by Development in Littoral Region – Effect of Sand Extraction around River Mouth”. Proceedings of the 8th General Seminar on Environmental Science & Technology Issues, Japan, Osaka, Nov. 2008, pp. 114-119.

• Ha Xuan Chuan (2009), “Assessing the effect of dredging activities”, Journal of Science & Technology Maritime, August 2009, p14-17.

• Trinh Cong Luan (2012).“Assess the impacts of river sand extraction on bank erosion and propose the prevention methods in Tien river – Co Chien river, Vinh Long province”, Master Thesis, Ho Chi Minh City University of Technology.

• Wiebe P. de Boer et. Al. (2011). “Impact of mega-scale sand extraction on tidal dynamics in semi-enclosed basin. An idealized model study with application to the Southern North Sea”, Journal of Coastal Engineer 58, 678-689.

• Dries Van den Eyde, Alain Norro (2009). “Modeling the effect of sand extraction on the Kwintebank”, European Marine sand and gravel group, May, 2009.

Reference

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