The flat area on either side of a stream's natural levee, where alluvium is deposited, is called the

Answer;

-Floodplain

The flat area on either side of a stream's natural levee, where alluvium is deposited, is called the foodplain.

Explanation;

-A floodplain is the area around a river that is covered in times of flood. A floodplain is a very fertile area due to the rich alluvium deposited by floodwaters.

-This makes floodplains a good place for agriculture. A build up of alluvium on the banks of a river can create levees, which raise the river bank. They are low-lying lands next to rivers, streams, and oceans. A floodplain is any land area susceptible to being inundated by water from any source.