Geography Reference
In-Depth Information
Making use of an amateur video from that night and from flood level inscriptions still
visible on some walls, some flood-affected locations were identified (Figure 9). Since it was
possible to recognize from the video the maximum flood levels, by means of a set of
in-situ
measurements the depth of water in those locations was estimated (Table 10).
Location (point)
Observed flood depth (m)
Simulated flood depth (m)
A
2.5
2.9
C
4.4
4.3
D
4.4
4.3
H
2.7
3.1
K
4.1
4.1
M
4.4
4.3
Table 10.
Comparison between the simulation results and the observed flood depths attained on the 3
rd
of December 1989 flood event.
Figure 9.
Location of places used to compare the simulation results and the observed flood depths
attained on the 3
rd
of December 1989 flood event.
4.4. Results and discussion
The 10- and 100- year flood area maps of the Tavira urban area show that a significant part
of the urban area which is adjacent to the Séqua/Gilão River is within the flood-affected
perimeter (Figure 10). The City's centre is severely affected both by the simultaneous
occurrence of high spring tide and the 10- or the 100-year rainfall events.
It is clearly visible that after the ST11 section the flood area expands widely. This is because
ST11 represents a heritage bridge which causes significant obstruction to the river channel.
A hydraulic gradient is formed by this bridge thus allowing water to overflow the river
channel.
