Which of the following contributes to the formation of coastal dunes?

The formation of coastal dunes is predominantly influenced by the transportation of sand by wind. This process begins when wind blows across loose sand, lifting and carrying particles from the shore and depositing them in mounds and ridges. Over time, as sand accumulates and vegetation starts to grow in these areas, it helps to stabilize the dunes, preventing erosion and further mobilization of sand.

While water flow from rivers, ice action, and groundwater movement may play roles in coastal environments, they do not directly contribute to the specific formation of dunes in the way that wind-driven sand transport does. Rivers primarily shape landforms through erosion and sediment deposition differently, ice action can reshape coastlines but does not create dunes, and groundwater movement mainly influences coastal geology rather than dune development. Thus, wind is the key force in creating and shaping coastal dunes.