a dale
A wide river valley is called a vale. In Scotland, a wide and flat river valley is also called a strath.
The proper name for a wide valley floor is typically referred to as the valley bottom or valley floor. It is the flat or gently sloping area between the valley walls where rivers or streams may flow.
An ancient under sea valley carved in the ocean floor is known as a canyon, usually given the name of the contributory river on the land. such as the Hudson Canyon, or the Clutha Canyon.
Indus River Valley.
The Nile gets its name from the Greek word "Nelios", meaning River Valley.
a mature river
A floor.
Krishna
The Nile River Valley and the Indus River Valley.
"The name Wyoming derives from the Munsee name xwé:wamənk, meaning 'at the big river flat,' but it was also named after the Wyoming Valley in Pennsylvania." [per Wikipedia]
The Nile River Valley got its name from the Nile River, which flows through the region. The ancient Egyptians called the river "H'pī" or "Iteru," meaning "great river" or "river." Over time, this name evolved into "Nile."
godawari river