ABSTRACT

Wakes, S.J.; Hilton, M.J., and Konlechner, T., 2016. Topographic steering of oblique incident winds across a foredune-parabolic topography, Mason Bay, Stewart Island, New Zealand. 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. 343–347. Coconut Creek (Florida), ISSN 0749-0208.

Climate change modelling predicts increased westerly winds across southern New Zealand, with incident winds becoming more oblique on many beaches. Of interest is the effect these increasingly oblique winds will have on beach-foredune sand flux and dune morphodynamics. We need to model wind flows over these dunes in order to understand these potential changes. Mason Bay, Stewart Island, New Zealand experiences a range of incident winds, from southwest to northwest and, therefore, provides opportunities to both model and verify topographic steering. The dune systems comprise of a large, topographically simple (Type I) foredune, backed by long-walled, discrete parabolic dunes. We use Computational Fluid Dynamics (CFD) to predict the behaviour of winds of a range of obliquities and infer sediment flow over coastal dunes. The wind steering across the dune system is also be explored through the numerical modelling. Results of modelling wind flow from a range of incident wind directions and boundary conditions are presented. The results indicate that oblique incident winds are topographically steered shore-normal across the foredune and inland parabolic dunes topographies. Future changes in wind direction might, therefore, have significantly greater implications for foredune development compared with hinterland dunes.

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