Geography Reference
In-Depth Information
Figure 11.36. Typical landscapes in Austria: (left) Alpine stream, (right) lowland stream. Photos: G. Blöschl, M. Zessner.
11.10 IMPLEMENTING THE EU FLOOD
DIRECTIVE IN AUSTRIA
r. merz, g. humer and g. bl¨ schl
Directive, and perform part of the flood hazard mapping.
The project was also motivated by an interest of the Aus-
trian Association of Insurance Companies (VVO) to obtain
a tool for premium estimation, as floods have recently
become insurable in Austria. The flood mapping project
related to a total of 26 000 km of streams in Austria and
consisted of three parts: estimation of flood discharges of a
given return period; estimation of inundation areas by
hydraulic models based on these discharges; and develop-
ment of an internet application to offer public access to the
flood hazard maps. This chapter is concerned with the first
step. Specifically, the aim was to estimate the flood dis-
charges associated with 30-, 100- and 200-year return
periods for a total of about 10 586 basins, most of which
are ungauged.
The issue from societal and hydrological perspectives
The European Flood Directive (2007/60/EC) was launched
in November 2007 to achieve a more integrated manage-
ment of the inland floods in the EU member states (EU,
2007 ). The Directive had been motivated by major
flooding in Europe, such as the 2002 and 2005 floods,
and a desire to manage floods in a more holistic way
involving structural measures such as flood protection
and non-structural measures such as flood warning and
flood alertness of the public. The Flood Directive required
all member states to carry out a preliminary assessment of
potential flood risk areas by 2011. For these areas, flood
risk maps need to be prepared by 2013 and associated
flood risk management plans need to be prepared by
2015. Specifically, Article 6 of the Directive stipulates:
'
Description of the study area
With an area of 84 000 km², Austria is hydrologically quite
diverse. The landscapes range from the lowlands in the
east, with elevations from 114 m a.s.l., to the high Alps in
the west, with the highest peak of almost 3800 m a.s.l.
( Figure 11.36 ). Mean annual precipitation ranges from less
than 400 mm/yr in the east to more than 3000 mm/yr in the
west, where orographic effects tend to enhance precipita-
tion. Land use is mainly agricultural in the lowlands,
forested in the medium elevation ranges, while alpine
vegetation and rocks prevail in the highest catchments.
Because of the diversity of hydrological processes, flood
generating mechanisms vary substantially across Austria
(Merz and Blöschl, 2003 ; Parajka et al., 2010a ). In the
Alps, runoff variability and floods are strongly affected by
snow and glacier melt. In the lower Alpine region south of
the Alps, snow is similarly important and snowmelt-
dominated floods often occur in May. However, the largest
Member States shall, at the level of the river basin district,
or unit of management
prepare flood hazard maps and
flood risk maps, at the most appropriate scale
'
and further:
'
Flood hazard maps shall cover the geographical areas
which could be flooded according to the following scen-
arios: (a) floods with a low probability, or extreme event
scenarios; (b) floods with a medium probability (likely
return period
100 years); (c) floods with a high probabil-
ity, where appropriate.
'
In Austria the Ministry of Agriculture, Forestry, Envir-
onment and Water Management started a national flood
mapping project known as HORA (HOchwasserRisikoflä-
chen Austria
Flood risk zones in Austria) to comply with
the preliminary assessment requirements of the Flood
-
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