Structures of which the primary aim is to change the longshore transport rates under both normal and extreme conditions are:
- Jetties / shore-normal breakwaters;
- Series of groynes;
- Detached shore parallel offshore breakwaters (emerged and/or submerged).
The above mentioned structures can all be observed along a Mediterranean coastal section of about 5 km in Sitges, Spain (Fig. 10.8). Open groyne cells with a spacing of about 500 m can be observed at the northern part of the beach and partly closed cells are present along the southern side of the beach. The harnessed solution with T-head groynes and detached breakwaters on the southern side is necessary to retain the beach sand within the cells (see further Sects. 10.5.3 and 10.5.4).