A case study in Switzerland is considered, where
hazard/flood maps are established as part of the planning of
flood protection measures. Due to the commune’s location
within a flat plain divided by a railway dike, it could be shown
that the settlements an d infrastructures are much more
endangered by floods than originally thought. Using the theme
“land cover” of the digital cadastral survey , a digital terrain
model (DTM) and bathymetry data, break lines were generated
to build a triangular mesh . Culverts, tubes and bridges are a n
important element of hazard mapping, as they can alter or
create new flow paths not only as common bottlenecks in the
channel ( overflow), but also outside in flooded settlement areas
where pedestrian/road underpasses and tunnels a re present
However, the modelling of culverts and tubes has revealed that
they are no longer suitable from a certain size of the channel, as
the flow passes by the point which define s the culvert. Thus,
several workarounds were tested to improve the relia bility of
the culverts/tubes Recorded floods have shown that buildings
are not necessarily an impermeable obstacle for the flowing
water. An approach was developed to consider buildings as
floodable as well as impermeable, as it could be observed that
lar ger building complexes may by traversed by floods and alter
the flow paths in this way. If these aspects are taken into
account, an informative hazard map may be established
