Question

Deposition of sediment occurs on the floodplain

A drop in base level of the river results in downcutting through deposits
Further downcutting occurs and the river abandons the previously formed floodplain
The oldest floodplain becomes isolated as the river downcuts, leaving a terrace.

Answer 1

Deposition of sediment on the floodplain occurs when a river widens and slows down. Downcutting happens when base level drops and the river abandons the floodplain. The oldest floodplain becomes isolated as the river downcuts, forming a terrace.

Step-by-step explanation:

Deposition of sediment occurs on the floodplain when a river or stream flows away from the source and the width of the channel widens, causing the current to slow. This slow-moving water allows for more sedimentation to occur. A drop in base level of the river can result in downcutting through the deposited sediment, and further downcutting may cause the river to abandon the previously formed floodplain. As the river downcuts, the oldest floodplain becomes isolated and is left as a terrace.