Final answer:
Seawalls are designed to keep seawater out of a place, while breakwaters cause waves to break earlier out at sea. Beach nourishment, sand dunes, and sand fences are likely to be damaged or washed away in a storm. Seawalls may need replacing most often.
Step-by-step explanation:
The type of coastal defense designed to keep seawater out of a place is a seawall. Seawalls are structures built parallel to the shoreline and are made of concrete or rock. They are intended to reflect or absorb wave energy and prevent erosion and flooding.
Breakwater systems are coastal defenses that cause waves to break earlier, out at sea. They are typically made of rocks or concrete blocks and are built perpendicular to the shoreline. Breakwaters create a protected area behind them where waves are less powerful.
The three types of coastal defense that are most likely to be damaged or washed away in a storm are beach nourishment, sand dunes, and sand fences. Beach nourishment involves adding sand to an eroding beach to restore its width and protect infrastructure. Sand dunes are natural formations of sand built up by wind and waves, and they provide a natural barrier against storms. Sand fences are installed on the beach to trap and accumulate wind-blown sand, helping to stabilize the dune system.
The type of coastal defense that may need replacing most often is a seawall. Seawalls are constantly exposed to wave energy, which can cause erosion and damage to the structure over time. Regular maintenance and repair are often needed to keep seawalls effective.