 |
| Titel |
The simultaneous occurrence of surge and discharge extremes for the Rhine delta |
| VerfasserIn |
Frank Selten, Sarah Kew, Geert Lenderink, WIlco Hazeleger |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081747
|
|
|
|
|
|
| Zusammenfassung |
| The low-lying Netherlands is at risk from multiple threats of sea level rise, storm
surges and extreme river discharges. Should these threats occur simultaneously,
a catastrophe will be at hand. Knowledge about the likelihood of simultaneous
occurrence or the so-called ‘compound effect’ of such threats is essential to provide
guidance on legislation for dike heights, flood barrier design and water management in
general.
In this study, which forms a contribution to the EU project ECLISE, we explore the
simultaneous threats of North Sea storm surges and extreme Rhine river discharge for the
current and future climate in a large 17-member global climate model ensemble. We use a
simple approach, taking proxies of North-Northwesterly winds over the North Sea and
multiple-day precipitation averaged over the Rhine for storm surge and discharge
respectively, so that a sensitivity analysis is straight forward to apply. By investigating soft
extremes, we circumvent the need to extrapolate the data and thereby permit the synoptic
development of selected events to be inspected.
Frequently, the joint probability between storm surges and extreme discharge for the present
climate is calculated assuming that each threat can be treated independently. This assumption
is based on the negligible correlation modelled between the sea level at the coast and river
discharge. But this assumption of independence lies at odds with intuitive reasoning, which
would connect both high surge-driving winds and heavy precipitation with the passage of
synoptic low pressure systems.
The presentation of the results allows the connection between the previous assumptions and
intuitive reasoning to be visualised. Our principle finding is that, for the current climate, the
probability of extreme surge conditions following extreme 20-day precipitation
sums is around 3 times higher than that estimated from treating extreme surge and
discharge probabilities as independent. For the future climate, the assumption of
independence cannot be rejected, at least not for precipitation sums exceeding 7
days. |
|
|
|
|
|
|