The phrase "a big river" is correct and usable in written English.
You can use it to describe a river that has a large size or significant volume of water.
Example: "The Amazon is known as a big river, flowing through several countries in South America."
Alternatives: "a large river" or "a vast river".
I have never lived away from a big river".
The tea-color Ponoi is a big river, at some points 300 yards across.
"It is like a big river of people, and if you stop the flow, you will have floods somewhere.
Uniquely for such a big river in the heart of tropical Asia, the biggest city along the Mekong's banks Phnom Penh has a mere 1.1m inhabitants.
They are a separate species from other kinds of bottlenose dolphins, whose presence in the lower reaches of a big river like the Hudson would be less alarming.
Here, the river crosses the city asymmetrically with a big river-bank in the south part (river-bank1 in Fig. 11), and a small one in the north part (river-bank2 in Fig. 11).
Fig. 11 A city (Zlin in Czech Republic) asymmetrically crossed by its river; forming a big river-bank in the south part (river-bank1 in figure), and a small one in the north part (river-bank2) in figure.
It was hoped the alkalinity would drop once it reached the Raba, a bigger river, but it was still between pH 9 and 10.
As the morning sky brightened, Lee forded a river, retrieved a single match (which would become important later), quartered 20 logs, climbed a small mountain, recited the American presidents, swam a lake, assembled the Legos, forded a bigger river and located an egg hidden in the woods.
Conrad's Heart of Darkness takes its readers on a hellish voyage up "a mighty big river... resembling an immense snake uncoiled... its tail lost in the depths of the land", but it begins opposite Gravesend in Kent, as Marlowe and his transfixed listeners wait on the Nellie, a cruising yawl, for the ebbing tide.
