* Waves and currents: Waves and currents carry sand and sediment along the coastline.

* Changes in energy: As waves slow down and lose energy, they deposit their sediment load.

* Sandbar formation: This deposition occurs in shallower water, often in areas where the water current is deflected or slowed down. Over time, these accumulations of sand build up to form sandbars.

Erosion plays a role in providing the sand for sandbar formation, but it's not the primary force in their creation. Here's how erosion contributes:

* Beach erosion: Waves can erode the coastline, providing the sand that is later transported and deposited to form sandbars.

* River erosion: Rivers can erode their banks and carry sand downstream, where it can eventually contribute to sandbar formation.

In summary, sandbars are created by deposition of sediment carried by waves and currents, while erosion provides the sand material for this process.