An Xbloc is a wave-dissipating concrete block (or "armour unit") designed to protect shores, harbour walls, seawalls, breakwaters and other coastal structures from the direct impact of incoming waves. The Xbloc model was designed and developed by the Dutch firm Delta Marine Consultants, now called BAM Infraconsult, a subsidiary of the Royal BAM Group in 2001 and has been subjected to extensive research by several universities. Benefits vs other systems Concrete armour units are generally applied in breakwaters and shore protections. The units are placed in a single layer as the outer layer of the coastal structure. This layer is called the armour layer. Its function is twofold: (1) to protect the finer material below it against severe wave action; (2) to dissipate the wave energy to reduce the wave run-up, overtopping and reflection. These functions require a heavy, but porous armour. Common factors to apply single layer concrete armour units are: natural rock is unavailable in required size or quality to withstand design wave or current loads quarry production is insufficient to match the material demand existing quarries are in uneconomic distance to project location road connections have load restrictions (bridges) and other bottlenecks, are in poor condition or congested Also compared to older concrete armour units, as e.g. tetrapod which are normally placed in double layer as for rock protection, modern single layer armour units (like the Xbloc and Accropode), involve significantly less concrete. Therefore, less construction material (cement, gravel) is required, reducing costs and also the carbon footprint of coastal protection works. Like Xbloc, most of these blocks are commercial developments and patented as such, Xblocs are not produced by the patent holder, but are fabricated and installed by a contractor who in return pays a license fee. Such an agreement involves certain technical support activities to ensure the correct application of the protection system. The patent expires in 2023, but although after that date anyone can make a block with this shape, one is not allowed to call it Xbloc, because the name is a protected trademark. Hydraulic stability and interlocking mechanism The Xbloc armour unit derives its hydraulic stability from its self-weight and by interlocking with surrounding units. Due to the highly porous armour layer (layer porosity of almost 60%) constructed with Xbloc units, the energy of the incoming waves will be largely absorbed. The Xbloc armour layer is therefore able to protect the rock