Alkema, Dinand 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Fig. 7 The detailed Digital Terrain Model that was Cot eintios, at Tent: 
used in the flooding simulations. Indicated are some (e dipped m 
important surficial features. SHY FERA eH 
+ 
indudrgi a — S. 
REE Axisis É 8. 
uu 
= 
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rentes Sn 5 
en "2 
Eom E E 3 
CERTES t D 
ue TET 2j 
Fireeumer iil 
Haba Mu 
kar ipshuntrd t c > 
a anm Fig. 8: The waterlevel as function of the discharge. 
Tree 
  
  
  
  
  
The discharge at Trento was over 1600 m?/s and the water level was about 5 meter above the reference level. 
At that time the Brenner highway, the Trento bypass and the Trento “interporto” were not yet constructed. For each 
simulation two detailed DTM were used: One representing the situation of 1966 (see fig. 9a and 10a) and another that 
represents the present topography (see fig. 9b and 10b). The reconstruction of the 1966 event is useful because it allows 
to validate the model results with the historic data as model validation. The simulation with the present topography 
shows how the discharge like the of 1966-flood would propagate if it happened in the present landscape. This allows to 
assess the effect of change in the flooded area due to these constructions. 
7 PRELIMINARY RESULTS 
The output of the model are water level maps and flow-velocity maps for every hour after the dyke-failure. These maps 
are used to obtain the following indicator maps: 
e time to flooding; 
e maximum water level map; 
e maximum flow velocity map. 
These indicator maps can be used to plan evacuation of inhabitants (the time to flooding indicates the time the 
floodwaters will reach a certain area). The water height map and the maximum flow velocity were multiplied to obtain a 
*mass-energy-map" 
If the vulnerability and the valueof the area are known the impact can be calculated for each scenario. The difference of 
impact can be attributed to the large structures (assuming other factors didn't change). 
From the results as shown in figure 9 it seems as if the constructions that are included in the map on the right-hand side 
(9b) have a positive effect on the time to flooding. The floodwaters seem to be delayed which can be considered a 
positive impact. 
When one looks at the “mass-energy” maps, (fig 10) the values are higher for the 1997 situation. The structures funnel 
the water such that they have higher flow-velocities and reach higher levels. So the extend of the flooded area may be 
less, the potential for causing damage in those area that are flooded is higher. 
These two examples show the complex nature of flood impact. Vulnerability studies and multi-criteria analyses will be 
needed to aggregate all possible impacts into a comprehensible impact assessment that can be included in an EIA. 
  
60 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.