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| Titel |
Macro-scale assessment of areas sensitive to changes in flood magnitudes for Austria |
| VerfasserIn |
Mathew Herrnegger, Benjamin Apperl, Tobias Senoner, Hans-Peter Nachtnebel |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094482
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| Publikation (Nr.) |
 EGU/EGU2014-9892.pdf |
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| Zusammenfassung |
| This contribution presents a GIS-based method for the identification of areas sensitive to
changes in flood magnitudes on the basis of existing flood maps and topographic features of
flood plains. The approach enables the identification of flood prone river sections for large
areas, as no additional hydrodynamic simulations are necessary or available. In our case
an area of ~84.000km2, including about 26.000km of rivers and streams, is
analysed.
Even though the results of climate models are uncertain regarding the prediction of future
changes in frequency and magnitude of floods, the recent accumulation of extreme flood
events in parts of Austria makes it inevitable to account for possible changes in runoff
characteristics. Therefore, an enhanced impact assessment of these changes and the
identification of flood sensitive areas is necessary.
The existing HORA data set (Natural Hazard Overview & Risk Assessment Austria)
indicates flood plains for recurrence intervals of 30, 100 and 200 years for the entire area of
Austria under current climate conditions. A variable climate change allowance is applied to
the corresponding discharges of the 200 years return period data set (HQ200), with the aim of
generating modified runoff values of equal recurrence intervals for all flood values (HQcc).
This procedure guarantees a consistent data set, based on the underlying Gumbel flood
statistics of the original data set.
The HORA-data sets includes points with the information on discharge and water depth
for the existing recurrence intervals. Based on the simplifying assumption of (1) a
rectangular cross section, (2) the water depth for the HQ200 discharge value and (3) the
modified HQcc value, a new water depth (hcc) and the change in water depth (Δh)
can be calculated for these locations. Changes in water depth are aggregated for
municipalities by calculating a weighted mean depth change, using discharge as
the weighting value. Based on the derived water depth changes, the existing flood
areas are enlarged on the basis of the digital terrain model with a resolution of
10x10m.
For every existing boundary point Pi(xi,yi,zi) of the HORA-HQ200 flood plain a change
in water depth Δh is added to the elevation value zi. For this point Pi all Points Pk,i in the
surrounding area r are identified, where the elevation value zk is lower than zi + Δh.
The surrounding area r, where valid points Pk,i can be situated, is defined by the
drainage area of the existing boundary point Pi. Pi therefore represents an outlet
point of a local subbasin. It is assumed, that points within the drainage area are
inundated with rising water levels beginning from the outlet point. Local flows are
thereby neglected. The derived flood plains look plausible and will be compared with
2-D hydrodynamic simulations for three case study areas in an on-going project. |
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