Mesoscale coastal complexity and its relationship to structure and forcing from marine processes

This study investigates Australiaʹs coastline complexity to establish the relationship between geological inheritance and ocean processes, as well as determine the characteristic length scales at which they operate. Each of Australiaʹs geological regions displays discrete complexity signatures indicating a correlation between coastal complexity and geology. These mesoscale complexity signatures can vary enormously, between regions over a range of length scales. An angled measurement technique is used to quantify coastal complexity for a large number of random nodes, at varying length scales, around the Australian continental margin. Cluster analysis are used to determine characteristic complexity ‘signatures’ for random nodes, and dimension reduction techniques and additive models are used to assess the relative effects of wave and tide power and physical variables in each geological region. However, although some geological regions are visibly distinct, all geological regions are comprised of up to three basic classes or typologies. Furthermore, this study demonstrates that at the mesoscale (1–100 km), geological inheritance has the major influence in determining coastal complexity. Results show lithological mix to be an important factor and coastlines of a homogeneous lithology tend to be straighter than coastlines of mixed lithology. They further demonstrate that wave action promotes a straight coastline if the lithology is homogeneous and a complex one if the lithology is heterogeneous This work will contribute to ongoing research in the classification of the Australian continental margin by utilising available geophysical datasets that are fundamental to the establishment of rigorous boundaries in the regional marine planning process. It provides important information about drivers responsible for coastal complexity at the mesoscale. It is only from such studies that constructive quantitative approaches can be developed for robust regionalisation of coastal and marine systems.