flood·gate /ˈflʌdˌget/
  水門,水閘,防潮水閘
  floodgate
       n 1: something that restrains a flood or outpouring; "suspension
            of surveillance opened the floodgates to illegal
            immigrants"
       2: regulator consisting of a valve or gate that controls the
          rate of water flow through a sluice [syn: sluicegate, sluice
          valve, penstock, head gate, water gate]