Morphological responses of a long-shore channel-shoal system in a mixed energy coast to a major storm
Abstract
The storm is a high energy event that can induce dramatic morphological changes of coastal channel-shoal systems in a very short period. However, the pattern and intensity of morphological change during the storm has high uncertainties due to the characteristics of local channel-system, sediment fraction and the mixture of tidal energy and wave energy. In this study, the mixed energy long-shore channel-shoal system (Nanpu channel shoal system in the Bohai Bay, China) on an open coast is chosen as an exemplary study area for the identification of relevant hydrodynamic drivers of morphology during the storm.
This study addresses the issue by applying a processes-based model, which considers multi-fraction sediment dynamics with four graduated grain-size fractions of 3, 30, 100 and 200 microns regarding strong spatial variations of mud-sand mixtures in the study area. This model is validated by field data, including the tidal level, the tidal current, and the suspended sediment concentration. The validated model is applied to hindcast the morphodynamic process of the channel-shoal system during a storm in October 2003 and identify the relevant hydrodynamic drivers by sensitivity tests. The hindcasting results illustrate that the tidal flat experiences severely erosion during the storm duration, while the long-shore channel is initially scoured with the growth of wind strength, then gradually accreted as the reduction of wind strength. The sensitivity tests quantify the impacts of wind intensity, wind direction and wave on the channel-shoal morphological changes, which indicate the tidal flat is subject to the wind-generated wave. Moreover, the wave-directed wind can enhance the erosion by 10 %. The erosion and accretion process of Nanpu channel is determined by wind-driven long-shore current and wave-induced offshore sediment transport respectively. But unlike the tidal flat, the erosion processes of channel are insensitive to the variation of offshore directed wind direction. In conclusion, this study not only identifies the relevant hydrodynamic drivers of morphological changes during the storm at the study area, but also reiterates the importance of wind in driving coastal storm response at the long-shore channel-shoal system.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS51D1286K
- Keywords:
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- 4504 Air/sea interactions;
- OCEANOGRAPHY: PHYSICALDE: 4512 Currents;
- OCEANOGRAPHY: PHYSICALDE: 4534 Hydrodynamic modeling;
- OCEANOGRAPHY: PHYSICALDE: 4564 Tsunamis and storm surges;
- OCEANOGRAPHY: PHYSICAL