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ABSTRACT
Kuroiwa, M.; Shibutani, Y.; Yasumoto,; Mase, H, and Matsubara,Y., 2016. Applicability of 3D beach evolution model with wave-current interaction to river-mouth bar formation. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 73-77. Coconut Creek (Florida), ISSN 0749-0208.
A coastal area model with wave-current interaction was presented, and then the performance and applicability of the numerical to morphodynamics around river mouths due to waves, wave-induced currents and river flows were investigated. First, model tests were carried out under a variety of wave and river discharge conditions to investigate their capability of predicting the formation of sand spit and terrace topographies. Second, model verification using a field site was conducted and the applicability was investigated. From the computed results, it was confirmed that the prediction of presented model had good qualitative agreement with an actual sand spit formation.
ADDITIONAL INDEX WORDS: Morphological change, river-mouth, numerical model.
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INTRODUCTION
River-mouth bars, such as sand spits, occur in river mouths connecting to sea areas with low tidal range mainly owing to wave action. If the river discharge is small, then the river mouth closes. The prevention of flooding due to heavy rains and maintenance of the function of the river mouth requires the control of river discharge and prediction of morphodynamics around river mouths. The flow field around a river mouth is extremely complex owing to river discharge, waves, waveinduced currents, and tidal currents of different densities. Therefore, it is difficult to predict the flow field and morphodynamics around river mouths.
Topographic features around river mouths are roughly classified into the three types following the work by Sawaragi (1995). (1) In a river-flow-dominating type, deltas and terraces form in front of the river mouth. (2) In a wave-dominating type, a river-mouth bar and asymmetric bars form under normal wave conditions. A longshore bar forms under an extreme wave condition. (3) In a tidal-current-dominating type, sand bars form in the river under high tide and high wave conditions. Furthermore, topographic patterns are classified into 11 types based on the characteristics of incident waves, discharge flows and tidal currents.
Many 3D morphodynamic coastal area...