Final answer:
The region where a river flows into a larger body of water is known as the river mouth or delta. It is an area rich in sediments like gravel, sand, and silt, and is crucial for the formation of habitats due to the mix of fresh and saltwater.
Step-by-step explanation:
The region where the river flows into a larger body of water is called the river mouth or delta. This area typically contains gravel, sand, and silt, and is characterized by lower energy levels compared to the rest of the river's course. An example of a river mouth is where the Mississippi River empties into the Gulf of Mexico. Deltas are important ecological areas as they often form rich habitats due to the sediment deposited by the river. This is also the zone where freshwater mixes with saltwater, creating a unique environment known as an estuary.his is the point where the river's flow meets the calm waters of the lake or ocean. At the mouth, the river usually widens, and sediment carried by the river settles, forming features like deltas or estuaries.