Masters Thesis Abstract: Javier Leon
Morphodynamics of Shelly Beach, Otago Harbour
The proposed investigation aims to explore the relationship between coastal processes and morphological response in order to understand the dynamics and evolution of a human influenced Holocene sandy barrier, Shelly beach – Otago Harbour, Dunedin.
The morphology and nearshore conditions of Otago Harbour are very dynamic and produce a constant infilling of the lower harbour. Ongoing dredging is needed to allow navigation. Port Otago Limited (POL) has been discharging the dredge spoil on three nearby dumpsites, including the nearshore of Shelly Beach.
Shelly Beach is a 750m wide fine-sand beach located immediately north of Otago Harbour. Once a highly dynamic sand bar, Shelly beach has been stabilized with the construction of a breakwater in 1884 and later by a low-tide training wall in 1906 to facilitate navigation through the tidal inlet.
The blockage of net sediment transport by the breakwater has caused chronic erosion in Shelly Beach. The trend reversal from reported serious erosion pre-1986 to net positive volumetric change of the dune/beach system from 1987 to 1993 was attributed to the positive effects of nourishments provided by the dredge spoil discharged by POL since 1986.
The main purpose of this study is to identify the links between processes, both anthropogenic (dredge spoil discharge) and natural (wind, waves and currents), and the mutual adjustment with the topography of Shelly Beach (nearshore, subaerial beach and dune system).
Building on the existing morphodynamic models, a conceptual model depicting links between processes and response will be formulated to explain sediment transport and the effects of dredge spoil discharge/nourishment on the beach system. Management implications can be identified and extrapolated to similar systems.