2. STUDY AREA 
The landslide risk assessment using GIS tools was 
methodologically processed within one map sheet in 1 : 
50 000 scale of the Czech cartographic system. This 
map sheet covers an area which has been heavily 
touched by various mining activities. The main activity 
is represented by brown coal mines. The above 
mentioned region is in the vicinity of Czech towns 
Usti-upon-Elbe and Bílina. The northern boundary is 
formed by the Erzgebirge Mountains. 
3. RELATED DATA 
Topographic maps in 1 : 50 000 scale, and 1 : 10 000 
scale were used for digital elevation model (DEM) 
creation. The geological map in 1 : 50 000 comprised 
90 geological classes. The hydrogeological map 
includes information about 16 hydrogeological classes, 
the pedological map has a long list with pedological 
units. The combination of all three types of data shows 
a large variety of natural conditions. These three maps 
in 1 : 50 000 scale were overlayed by the existing 
landslide map which comprised both recent and passive 
landslides from the Czech Geological Archive. It was 
found that nearly 90 per cent of all landslides are 
situated in tailings or recclamation morphological units 
and very often in the vicinity of water basins or 
streams. 
Classes of these three groups were regrouped 
according to newly attached weight values. The values 
varied from 1 (no landslide susceptibility) to 4 (high 
landslide susceptibility) for geological, pedological and 
hydrogeological classes. The areas with highest 
landslide susceptibility (value 11, 12) were chosen to 
be studied in detail from the point view of slopes and 
directions of slopes. The creation of a digital terrain 
model showed to be very important for a relevant 
landslide risk assessment analysis made in larger scale 
than 1 : 50 000. The digital terrain model would have 
excluded areas which, even with high landslide 
susceptibility (>8) studied from geological maps are 
stable due to slope conditions on one hand, and would 
have stressed areas which are still untouched by 
landslides, but with high landslide susceptibility (>7) 
and of high landslide risk due to sloping on the other 
hand. 
The digital terrain model was created from 1 : 
10 000 topographical maps and from a stereo pair of 
aerial photos. 
4. DIGITAL TERRAIN MODEL 
4.1 The reference DEM 
The reference DEM with a very good spatial resolution 
(the identical scale as the landslide changes) must be at 
the disposal of users in a useful raster or vector form. 
For the Czech Republic, a scale 1: 5000 - 10 000 is 
considered as sufficient. A detailed DEM was created 
in the past from the digital mapping in urban areas, but 
it is necessary to create the DEM for other areas which 
are endangered by landslides. It is carried out by by 
means of digitalization of the existing topographic 
maps. Elevation contours from 1 : 10 000 are 
vectorized and stored to files of related types of data 
A derivation of the DEM from the old 
photogrammetric stereo images is another possibility of 
the reference DEM creating. In this case, the DEM is 
made by using a method of automatic image correlation 
of floating image submatrices. It is used for the creating 
of an orthophoto. Finally, the DEM of a selected area is 
stored in a raster form for a more accurate GIS 
analysis. 
4.2 The new DEM 
The new DEM of a selected area can be created by 
classical geodetical methods (tachymeter, total station) 
588 Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
  
on 
de 
ste 
fli, 
siz 
SC: 
spé 
dat 
det 
ver 
(in;