It will gradually slow down and the river will pick up and move additional sediment.
A is an area of land where a river enters a lake of sea?
Mouth of a River
Delta
delta
A Delta.
The mouth is where the river enters the sea.
It enters Utah West of Grand Junction and flows past Moab joining the Green River on its way to Lake Powell where it enters Arizona near Page.
sandbars
deltas
It is the river's mouth
There is no general term for the connection between a lake and the ocean that it is an arm of. The area where a river or stream enters the ocean is a mouth, also possibly a delta or an estuary.
riverine island