Alluvial soil and riverine soil are essentially the same thing. They are both synonymous terms.

Here's why:

* Alluvial soil is soil formed by the deposition of sediments carried by rivers. These sediments are typically sand, silt, and clay, and they are deposited along the riverbanks, in floodplains, and in river deltas.

* Riverine soil is a term used specifically for soils that are directly influenced by rivers. The word "riverine" emphasizes the close connection to the river's water and its flow.

Therefore, alluvial soil is called riverine soil because it is formed by the action of rivers and is directly related to river ecosystems.