Thesis: An investigation of the nearshore hydrodynamics on contrasting open-coast and reef-protected beaches in Western Australia
Nearshore hydrodynamics govern a large number of processes, including the transport of coastal sediment, pollutants, nutrients, larvae and swimmers with implications for the management of shoreline development, ecosystems and beach safety. Hydrodynamics in the nearshore zone are primarily driven by waves and wind, but they are strongly affected by the bathymetry. Western Australia features a large variety of coastal geomorphology, ranging from alongshore uniform beaches, small scale limestone reefs, to large scale fringing coral reefs (e.g. Ningaloo Reef). The complex bathymetry in reef environments introduces circulations similar to rip currents that are typically much stronger than along sandy beaches. The difference in scale of rocky limestone and coral reefs is likely to affect the strength and form of these circulations. However, little research has been undertaken in rocky coast environments, despite estimates indicating that up to 33% of the world’s coastline is rocky.
Historically, the influence of the wind on nearshore hydrodynamics has been primarily studied in low wind environments and in terms of the direct wind stress. This research project will investigate the effect of wind in the strong sea breeze climate of South-Western Australia and will also quantify the effect of wind on the wave breaking process which may ultimately alter wave-driven currents.
Collectively, these research gaps will be addressed through the analysis of new and existing field data of wave, wind and currents on both a local open-coast sandy beach and on contrasting reef fringed beaches.
Why my research is important
Hydrodynamics in the nearshore zone are the key driver of transport and exchange processes between the coastal zone and the inner shelf. They control the fate of material including sediment, pollutants, nutrients and larvae and are important for the connectivity of the coastal zone and the inner shelf. Nearshore currents may also constitute a hazard to swimmers that may be pulled offshore in rip currents.
The proposed research will help to improve numerical models for nearshore applications with respect to wind effects and complex bathymetries. It will provide the research community with much needed field data on limestone reef environments that will help to understand these environments better and to calibrate numerical models to simulate the flow in these environments. An improved understanding of nearshore hydrodynamics in general will aid to predict the distribution of tracer material and can contribute to other fields of study where knowledge of transport pathways is crucial (e.g. morphology and ecology). Applied in morphological, ecological and safety studies the improved knowledge of hydrodynamics will ultimately lead to better shoreline erosion, beach safety and environmental management practices.