buttress dam
dam with a solid, water-tight upstream side that is supported at intervals on the downstream side by a series of buttresses or supports
en-GB/ˈbʌtɹəs ˈdæm/
en-US/ˈbʌtɹəs ˈdæm/
dam with a solid, water-tight upstream side that is supported at intervals on the downstream side by a series of buttresses or supports