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The study of salt intrusion, land use and rice yield in the coastal plain of the Mekong delta (Vietnam) based upon field work, remote sensing and GIS

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Dutch title: Studie van zoutintrusie, landgebruik en rijstoogst in de kustvlakte van de Mekong Delta (Viëtnam) gesteund op veldwerk, teledetectie en GIS
Reference no: T4/DD/12
Period: December 1996 till November 1998
Status: Completed

Thesaurus terms: Deltas; GIS; Remote sensing

Institutes (2)  Top 
  • Universiteit Gent; Faculteit Wetenschappen; Vakgroep Geografie; Afdeling Landschapskunde en milieuzorg, more
  • Belgian Science Policy (BELSPO), more, sponsor

Abstract:
Objectives:

The development of the Mekong delta is an urgent matter for the Vietnamese authorities. It is aimed to improve the cultivation of rice in order to meet the food supply for the increasing population and to stimulate the export facilities for rice. Moreover, large-scale public works are foreseen, including the deepening of the estuary to improve the accessibility of the area. The coastal plain of the Mekong Delta is subject to a severe degree of salt penetration through the major rivers (Mekong, Bassac,...) and creeks that infiltrates in the soil. These salty intrusions form a limiting factor for the development of the rice cultivation.
HAECON n.v. is studying the possibilities for the deepening of the estuary. Questions arise what will be the implications of this deepening on salt intrusions and the agricultural production in general, and for the rice production more specifically. Therefore a better knowledge and mapping of the land use, with emphasis on rice cultivation, is needed.
This project aimed to build a user-friendly tool for the detection and the modelling of salt water penetration in macro-estuaria characterised by a tropical hydrology and to evaluate the usefulness of remote sensing in the research of hydro-sedimentological processes of prodeltas.

Methods:

1. Literature review to define the system requirements for remote sensing and GIS in function of saline water intrusion in estuaria and delta-system of the humid-tropics.

2. Fieldwork to: (1) define the relation between saline intrusion, landuse/land cover and geomorphology, (2) set up an interpretation key for supervised classification and (3) measure the salinity, speed, sediment load in the Bassac river.

3. Preparation of the GIS in ILWIS and ER-MAPPER, including: topography, soil type, salinity intrusion, influence of tides, land use/land cover. These layers will be used to set up the basic scenario for the Mekong delta regarding the salinity intrusion.

4. Application of radar-technology for the mapping of the hydrosedimentological evolution in the Mekong delta and prodelta (inundated areas, sediment plumes) : Supervised image classification and calculation of change indices.

Results:

The starting point for the basic scenario regarding the salinity intrusion is the salinity model obtained through the TELSAT III program (Ismailia, Egypt). This model had to be adapted since the source of salinity does not correspond with the salinity source in the Mekong delta. Additional information necessary in the model are: influence of tides (distance to the South-China Sea), influence of intrusion (distance to the main rivers - Mekong and Bassac). During the two field campaigns, it became clear that salinity problems occur mainly in the depressions bordered by sandbars (former coastal ridges). These areas are restricted for the cultivation of rice (one crop/year). The model for salinity intrusion is set up for a test area to the NE of Can Tho. For this area topographical maps (with altitude indications in dm) were available. The obtained result showing zones with high probability for salinity intrusion correspond to a large extent with the ground truth (field survey). One of the major restrictions in the model is the need for highly detailed altitude information (because of extremely level character of the land and the importance of micro-relief).

Deliverables: model of salt water intrusion, (analogue/digital maps): DEM, soils, land use/land cover, inundations, 3D views.

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