On land, a hurricane is no longer powered by evaporating seawater, so it slowly weakens. Before the hurricane weakens, however, it may cause significant damage to the area over which it passes. Intense winds and rainfall can damage homes and other buildings and knock over power lines and trees. Winds and low pressure can also affect the ocean, causing large waves called storm surges to flood the coast. These surges can cause erosion, the carrying away of sand from the beach to other locations. As the beach erodes, it becomes narrower and more vulnerable to future hurricanes.