 |
| Titel |
How do storage and drainage processes influence extreme floods in the Swiss Alps? |
| VerfasserIn |
Maarten Smoorenburg, Nina Volze, Michael Margreth, Simon Scherrer, Felix Naef |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081492
|
|
|
|
|
|
| Zusammenfassung |
| Comparison of extreme flood runoff hydrographs in steep mountainous catchments in the
Swiss Alps reveals large differences in the capability of catchments to dampen runoff
formation. In some catchments a dampened runoff response is observed with a threshold-like
reaction to very extreme rainfall inputs, whereas in other catchments this threshold-like
behavior is already observed during much smaller storms, or has not been observed at all. The
threshold-like behavior makes estimation of flood risks with long return periods highly
uncertain. Therefore, understanding of dampening mechanisms is key to assessing catchment
vulnerability to extreme events.
We present typical flood responses in various mountainous catchments and try to explain
what types of geomorphological features have enough storage potential to cause the observed
dampening of the runoff formation. The dampened reaction at the catchment scale results
from the spatial distribution of these geomorphological features in the landscape and how
water is stored and drained. For better understanding of the storage and drainage processes
and timescales, we have measured runoff in springs and headwater catchments dominated by
geomorphological features with large storage potential, such as talus slopes, moraines and
deep-seated creeping landmasses. Additional insights were obtained from a large scale
sprinkling experiment on a creeping landmass slope (135 m2) and groundwater observations
in its fissured-rock subsurface. The measurements show how these geomorphological
features, even in steep terrain, may hold water long enough to cause a dampened flood
response.
To transfer these insights to the catchment scale, a mapping scheme was developed to
delineate the areas with large storage potential and rank their drainage intensity. The mapping
scheme benefits much from combing new data sources like high resolution digital elevation
models (2 m by 2 m), aerial photographs and detailed geo(morpho)logical maps. The scheme
was used to produce dominant runoff process maps in catchments with varying degrees of
dampening of the flood runoff formation. A conceptual hydrological model for flood runoff
simulation was developed based on these maps and the processes relevant for runoff
formation. The parameterization of the model was based on observed behavior at smaller
scales and the model performance was evaluated at the catchment scale. It was found that the
distribution of large storages can explain the observed differences in runoff generation in the
studied catchments.
Also, it was researched whether these large storages are responsible for sustaining
baseflow during extremely low flow conditions. Recession analysis shows that this is
possible, but that other factors may also govern the low flow behavior. |
|
|
|
|
|
|