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Erosion and accretion in the coastal zone

Professor Mai Trong Nhuan, Dr. Nguyen Hoan and Dr. Vu Van Phai

Pho Lueu Truong, Hanoi University of Science, Vietnam National University, 90 Nguyen Trai Road, Hanoi, Vietnam. Tel: 84 4 8588739. Fax: 84 4 8583061. Email: mtnhuan@it-hu.ac.vn.

Abstract of paper presented at the conference Environmental Change and Vulnerability: Lessons from Vietnam and the Indochina Region, Hanoi, Vietnam, April 4-5th 1998.


The main factors affecting erosion and accretion in the study area of the Red River Delta are as follows: sediment supply and balance; river activities and tidal regime; sea-level rise; sea wave and currents (direction, speed, etc.); geodynamical conditions; erosional resistance of rocks; and human activities (sea and river dam and dike construction, mining, deforestation, etc.).

Accretion occurs in the main part of the coastal zone (more than 60%). The intensity of accretion has increased from the Xth century to the XXth century (from 30-40m/year to 100m/year). Thanks to accretion, the coastal zone is expanding rather strongly, especially in the Bach Long area 1152 ha/year; the Tra Ly area, 812 ha/year; and the Nam Hung area, 600 ha/year. Accretion results in rapid changes of river mouths, change in shoaling of access channels, increased land area and mineral placers, appearance of new ecosystems and new habitats, and intensive exchange of nutrients between land, sediment and sea water.

The area suffering erosion (40% of the coast) is less than the accretion area. The highest erosion intensity occurs in the Giao Phong area, 33.3m/year. The intensity of erosion in the areas of Nghia Phuc and Giao Long is the lowest, 7.8 - 8m/year. Erosion in the study area results in damage of constructions and ecosystems, decrease of the coastal zone (affecting agriculture, transportation, living and bathing places).

For accretion and erosion control, as well as for coastal zone integrated management, it is necessary to carry out monitoring, to model sedimentation and erosion processes, to propose optimal prevention methods, and to study geodynamic, hydrodynamic and other relevant characteristics of the coastal zone.


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