At site 1, three groins are constructed. What would happen to the beach if five groins were not constructed over the same distance?

Groins and jetties are walls or barriers built perpendicular to the shoreline. Groins are much shorter structures built on straight stretches of beach away from inlets. Groins are intended to trap sand moving in longshore currents. They can be made of wood, stone, concrete, steel, or fabric bags filled with sand. Some designs are referred to as T-groins because the end of the structure terminates in a short shore-parallel segment. Both groins and jetties are very successful sand traps.

If 5 groins are not constructed over the same distance, it may not be able to trap sand properly and the beach may lose sand slowly to the ocean. The length of the groyne is designed in order to trap a fraction of the transport.