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| Titel |
Evaluation of wave conditions and morphological response linkage for establishment of a set of storm impact thresholds |
| VerfasserIn |
Ekaterina Trifonova, Nikolay Valchev, Nataliya Andreeva, Petya Eftimova |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041212
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| Zusammenfassung |
| Storms are one of the phenomena determining the short-term evolution of the coasts. Certain
storm conditions can cause severe beach erosion, partial or complete destruction of coastal
structures and human life and occupation. The majority of the unfavourable consequences
could be mitigated by means of early warnings. This implies establishment of a set of
thresholds triggering critical morphological response.
The study explores a linkage between the wave conditions and morphological changes
along the western Black sea coast. The methodology is based upon the interdependence
between hydrodynamic factors (wave energy and wave induced flow), lythodynamic response
(sediment transport) and morphological effects (sea bad evolution, shoreline retreat).
The sea state history in representative offshore locations is reconstructed through
hindcasting. The morphological changes are assessed using long-term series of coastal
measurements. Furthermore, for a couple of storms there is evidence for damages on coastal
infrastructures.
It is found out that the thickness of the eroded layer seems to be more responsive feature
with respect to the variation of the storm intensity. Moreover, in most of the cases, the more
energetic the event, the larger the bottom erosion. For that reason, this feature’s behavior is
considered more useful for definition of the threshold for significant beach change.
The sea bed erosion of the order of 0.4-0.5m is considered typical for seasonal
variations to which corresponds a retreat of about 2-4m, for which the profile shape is
observed to be recovering during the post storm period. However, the measured profile
deformations and shoreline displacement after a particular storm (January 1977)
greatly exceeded the usual seasonal course. On the whole, it is assumed that the
majority of storms are not intense enough to call forth hazardous effect. Therefore,
only storms with intensity similar to that of January 1977 or February 1979 are
considered capable of generating damages to infrastructure and possible threat to human
lives.
The set of threshold for morphological impact of the storms can be described in more
details as follows. The first critical value, called initial wave threshold, accounts for
wave conditions (significant wave height, mean period and mean direction of wave
propagation) causing intense sediment transport. The storm thresholds determining
significant morphological changes and morphological damage are established by
consideration of integrated wave energy accounting for both wave pattern and storm
duration. As a result, it is concluded that storms with integrated wave energy between
0.30 - 0.66x106 Jm-2 can produce important morphological changes, while more
energetic storms are considered extreme events with high destructive potential. |
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