Morphological Response of Submerged Structures on a Highly Dynamic Wave Dominated Beach

Multi-purpose submerged coastal protection structures are increasingly being considered on sandy wave dominated coasts for their relatively low impact on visual and beach amenity compared to traditional emerged structural works such as breakwaters. However, knowledge of submerged coastal protection structure attributes, with respect to their impact on morphological responses, is scarce, mainly due to the difficulty in predicting outcomes in dynamic environments and a reliance on expensive laboratory or numerical modelling experiments combined with a general lack of in-situ monitoring data. The design and performance of multi-purpose submerged coastal protection structures for coastal protection and surf amenity is assessed here using a process-based model. The model is supported by field measurements used to calibrate models of two existing Gold Coast artificial reefs and nearshore beach nourishments and their morphological evolution. Twenty-five scenarios with varying crest width, shape, depth and distance offshore were tested to identify key physical parameters for the effective and efficient design of submerged nearshore protection structures. The open coast beach of the northern Gold Coast was used as a case study site however this research methodology can be used to inform coastal protection strategies for other wave-dominated, sandy beach coastlines with similar geology, geomorphology, tide and wave climate. The impacts of the submerged structures on nearshore waves, hydrodynamics and morphology were determined in several key areas such as the lee of the structure, updrift and downdrift active profile regions. The results demonstrate that validated morphological models can be applied with increasing confidence to develop evidence-based guidelines for defining the key planning, design, and structural parameters of nearshore coastal protection structures to achieve effective coastal protection and enhanced recreational amenity outcomes. ; Full Text