The landform often formed at the mouth of a heavily silted stream is called a delta.

Here's why:

* Silting: As a river flows, it carries sediment (silt, sand, and other materials) downstream.

* Mouth: The mouth of a river is where it enters a larger body of water, like a lake or ocean.

* Deposition: When the river reaches its mouth, the velocity of the water slows down. This causes the sediment to be deposited, building up over time.

* Delta Formation: This deposited sediment forms a triangular-shaped landform, often with multiple channels, which is called a delta.

Think of the Nile Delta in Egypt or the Mississippi Delta in the United States as classic examples.