"Opened floodgates" is a phrase often used to describe a sudden influx or release of something, usually undesirable. There are several synonyms for this phrase, including "unleashed," "unbridled," "uncontrolled," "deluged," "overwhelmed," "inundated," and "swamped." These words can be used interchangeably to convey the same idea of a sudden and overwhelming surge of something. For example, if a government decision leads to an influx of immigration, it could be described as "opening the floodgates of immigration" or "unleashing a deluge of new arrivals." These synonyms can be used to add variety and nuance to language, avoiding repetition and providing a more descriptive and engaging writing style.