The 12th International Conference on Scour and Erosion (ICSE 2025)

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.