River

It divides line between one river basin and the next.

Smaller rivers join the main one.

Where the river starts.

The point where two rivers join.

The flat land beside the river.

Rain falling in the area inside the red dashed line feeds the river.

This is where the river flows into a lake or the sea.

The water dissolves soluble minerals from the bed and banks.

Rocks and stones and sand in the water act like sandpaper.

The rocks and stones wear each other. They bang together and knock bits off each other.