| The Flemish Ardennes (W Belgium) are known to be affected by deep-seated
landslides. The assessment of the landslide reactivation hazard requires
understanding the driving processes and delimiting precisely not only the
landslide boundaries but especially that of their most active parts.
Precise 3D models of 13 landslides were produced by digital
stereophotogrammetry using aerial photographs of different dates. Dealing
with photographs at the scale 1:25000 or larger, we obtained for each
model an accuracy better than 0.5m.
As a first result, the main size parameters of the landslides (width,
length, depth, volume, ...) are easily computed.
Moreover, the obtained DTMs may be subtracted from each other in order to
determine the apparent vertical displacement of each pixel during the
interval of time considered. Provided that more than 2 epochs are
documented, such DTMs not only supply precise information about distribution
and style of the landslide activity but may also point to temporal
variations in this activity.
The subtraction of DTMs allows us to give an estimation of the volume of the
"uplifted" and "collapsed" terrains between two epochs. |