From Longman Dictionary of Contemporary Englishdrainagedrain‧age /ˈdreɪnɪdʒ/ ●○○ noun [uncountable] TBCthe process or system by which water or waste liquid flows away A handful of pebbles in the bottom of a flowerpot will help drainage. a plan to improve the town’s drainage system
Examples from the Corpus
drainage• Together with Thames Water, it's just finished a £350,000 drainage project for the Middleton Road area.• drainage ditches• Gas and drainage pipes had broken as a result of the settlement and there was a risk of further breaks.• And where proven strength and reliability are called for, clay drainage is its own guarantee.• Farm drainage ditches ensure that water runs directly into streams rather than being filtered through the soil.• Much of it is below sea level and only innumerable drainage ditches prevent it from reverting to its natural state.• There were no drainage ditches here, the shoulders too abrupt, the slope too precipitous, to collect water.• About 80 percent of the drainage goes to a treatment plant and about 20 percent flows to these waterways.• The drainage system over some sections of route has also had to be refurbished or renewed. 