Investigation by satellite imagery of parameters determining the vulnerability of dykes in Vietnam

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Programme: TELSAT 4
Contract: T4/12/56
Start - End: 31 mars 1999 - 29 avril 2000

Context and objectives

In the region of Hanoi, in North Vietnam, numerous earth dykes built over a hundred years ago hold back the waters when there are major floods of the Red River during the period from the end of July to the end of August. In that period the local authorities and the inhabitants are on constant alert due to the genuine danger of a breach. It is thus useful to know whether remote detection can contribute valuable information on this subject, given the surface area and the number of dykes to be monitored.

The object of the present study therefore consists of establishing the potentials for using remote satellite detection, and notably radar imagery and its interferometric derivatives, for identifying the vulnerability of earth dykes in North Vietnam. The zone of study is restricted to a portion of the Duong River.

Project outcome

Expected scientific results

  • The SPOT Xi image and the SPOT-ERS/PRI combinations allow one to individualise the dykes, the sheets of water and the irrigation canals. The merger of a pair of RADARSAT images and their normalized difference also produces a good result.
  • The vulnerability of the dykes appears identifiable on the SPOT and SPOT-ERS images classified according to the presence of sheets of water outside the dykes and discontinuities in their level. These could indeed be due to leaks and openings.
  • The ERS PRI images make it possible to highlight the changes of humidity at the surface of the ground between two dates, while at the same time raising a problem of calibration of these images.
  • Use of the interferometric DTMs at our disposal is not conclusive for identifying the dykes and their morphology.
  • Use of one-day coherence images opens up several possibilities because the observation of a weak value would indicate a significant change of the dykes between two dates.
  • A reconnaissance mission in the field conducted parallel to a series of acquisitions of images spread over a longer time period proves necessary in order to validate and extend our observations.
    • Project leader(s): ULg - Gembloux Agro-Bio Tech - Echanges Eau-Sol-Plante
    Location: Region:
    • North Vietnam
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