A range of seawall types can be envisaged in relation to wave energy, resembling cliff and beach profiles. Vertical seawalls are built in particularly exposed situations. These reflect wave energy and under storm conditions standing waves (clapotis) will develop. In some cases piles are placed in front of the wall to lessen wave energy slightly. Curved or stepped seawalls are designed to enable waves to break and to dissipate wave energy. The curve can also prevent the wave overtopping the wall, and provide additional protection for the toe of the wall.
A series of rubble mound-type structures (revetments, riprap) are used in less demanding settings. The least exposed sites involve the lowest-cost bulkheads, or revetments of sand bags or geotextiles. These serve to armour the shore and minimize erosion. They may be either watertight, covering the slope completely, or porous, to allow water to filter through after the wave energy has been dissipated.
The barrier was initially completed in 1735. Over the years, the French continued to fortify the wall, piling huge boulders along its 1.25-mile (2-kilometer) coastline to stop erosion from the waves pounding the harbour. At its highest, the barrier running along the water's edge reaches about 27 feet above sea level. The boulders, some weighing up to a ton, are weathered black and brown. The sea wall is inspected every year. Whenever gaps appear or the stones sink into the sand, the government adds more boulders to keep it strong.
The Union Territory of Pondicherry recorded some 600 deaths from the huge tsunami waves that struck India's coast after the mammoth underwater earthquake (which measured 9.0 on the moment magnitude scale) off Indonesia, but most of those killed were fishermen who lived in villages beyond the artificial barrier.