Seawall

A seawall is a rigid coastal defense structure built along a shoreline where the sea acts directly on the land, intended to protect areas of human habitation, conservation, or leisure use from the action of waves, tides, and tsunamis, typically constructed from reinforced concrete, boulders, steel, or gabions. Because a seawall is a fixed, hard structure, it works by reflecting wave energy rather than absorbing it, which can cause scouring at the wall's base and worsen erosion on neighboring stretches of coast that the wall does not protect. Seawall construction dates back thousands of years; the oldest known coastal defense structure, a roughly hundred-meter row of boulders off the coast of Israel, was built about seven thousand years ago to counter post-glacial sea level rise, and the Romans built a seawall at Caesarea Maritima around the first century BC using their own pozzolana concrete. Modern seawalls often double as promenades or recreational walkways in addition to their protective role.