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Physical Modelling of Scour and Scour-Induced Settlement of a Modular Artificial Reef

Modular artificial reefs play a critical role in coastal engineering by enhancing marine habitats
and protecting shorelines against coastal erosion. However, the presence of these structures can
induce significant local scour, which may compromise their integrity and effectiveness. To
better understand the effect of local scour on artificial reefs, experimental testing was
conducted to determine the likely scour and scour-induced settlement of artificial reef modules
due to longshore tidal flow. Reduced-scale (1:5) physical model testing of different
arrangements of modular artificial reefs were conducted comprising modules developed as part
of the Defense Advanced Research Projects Agency (DARPA) Reefense project: A Mosaic
Oyster Habitat for Coastal Defense. The model scale reef modules were formed from concrete
with three different heights (equal to 1/3, 2/3 and full height). The testing revealed that scour
and settlement are likely to occur for each of the arrangements tested. The majority of scour
and settlement was observed at the corners of the arrangements, resulting in some modules to
settle and translate into a scour hole. The use of reduced height modules at the edges of the reef
appeared effective in mitigating scour-induced settlement of the modules for the range of
conditions considered in this testing.