open the floodgates idiom
引发更多同类事件;放开限制
If an action or a decision opens the floodgates, it allows something to happen a lot or allows many people to do something that was not previously allowed.
Officials are worried that allowing these refugees into the country will open the floodgates to thousands more. 官员们担心，允许这些难民入境会引发数千其他难民的涌入。