'drainage channel' is a correct phrase and can be used in written English.
It refers to a channel or pathway designed for the purpose of directing or carrying away excess water or other fluids. Example: The city's drainage system was not well-maintained, causing the drainage channels to become clogged and resulting in flooding during heavy rains.
Raw sewage leaked onto the beach from a drainage channel.
There, it hopped into a drainage channel for an even steeper drop.
An underground drainage channel dumps wastewater through a pipe into the canal behind the school.
As a result, streams began flowing westward down from the Rockies, and found the earlier drainage channel.
Because of the many roads in the area, the brook has become a drainage channel for runoff and is carpeted with debris, Mr. Schneider said.
To ease pressure on the unstable barrier, soldiers have spent the past week digging a 475-metre-long drainage channel near the site in Beichuan county.
The river valley was once marshy, but a drainage channel built in the 1930s has made its rich soils highly suitable for agriculture.
By foregoing a full environmental review, taking a direct route, and leaving out clean-up measures, the state has built a 14-mile drainage channel for only $28m.
At the moment, Mr. Solomon said, the airport would like to build a small drainage channel to remove water seeping from a nearby lake; the water is encouraging plant growth that attracts birds, which in turn endanger landings and takeoffs.
I pointed out that the Assi River, a thirty-foot-wide drainage channel that flows into the Ganges just upstream of Assi Ghat, bypasses the pumping stations and pours raw sewage into the river.
He told the Associated Press that the area where Clinton's clot developed is "a drainage channel, the equivalent of a big vein inside the skull it's how the blood gets back to the heart".
