Morphological and sedimentological response of a mixed-energy barrier island tidal inlet to storm and fair-weather conditions
The environment of ebb-tidal deltas between barrier island systems is characterized by a complex morphology with ebb- and flood-dominated channels, shoals and swash bars connecting the ebb-tidal delta platform to the adjacent island. These morphological features reveal characteristic surface sedimen...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-06-01
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| Series: | Earth Surface Dynamics |
| Online Access: | http://www.earth-surf-dynam.net/2/363/2014/esurf-2-363-2014.pdf |
| Summary: | The environment of ebb-tidal deltas between barrier island systems is
characterized by a complex morphology with ebb- and flood-dominated channels,
shoals and swash bars connecting the ebb-tidal delta platform to the adjacent
island. These morphological features reveal characteristic surface sediment
grain-size distributions and are subject to a continuous adaptation to the
prevailing hydrodynamic forces. The mixed-energy tidal inlet Otzumer Balje
between the East Frisian barrier islands of Langeoog and Spiekeroog in the
southern North Sea has been chosen here as a model study area for the
identification of relevant hydrodynamic drivers of morphology and
sedimentology. We compare the effect of high-energy, wave-dominated storm
conditions to mid-term, tide-dominated fair-weather conditions on tidal inlet
morphology and sedimentology with a process-based numerical model. A
multi-fractional approach with five grain-size fractions between 150 and
450 μm allows for the simulation of corresponding surface sediment
grain-size distributions. Net sediment fluxes for distinct conditions are
identified: during storm conditions, bed load sediment transport is generally
onshore directed on the shallower ebb-tidal delta shoals, whereas
fine-grained suspended sediment bypasses the tidal inlet by wave-driven
currents. During fair weather the sediment transport mainly focuses on the
inlet throat and the marginal flood channels. We show how the observed
sediment grain-size distribution and the morphological response at
mixed-energy tidal inlets are the result of both wave-dominated less frequent
storm conditions and mid-term, tide-dominant fair-weather conditions. |
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| ISSN: | 2196-6311 2196-632X |