Ⅰ.
open the floodgates (to sb/sth)
► to make a lot of people do something by removing a rule that stopped it being possible before, especially when you do not want this to happen: »
Banks feared the legal action could open the floodgates for customers to sue over high fees.
Main Entry: ↑open
Ⅱ.
open the floodgates (to/for sth)
► to allow a new situation or activity to develop and become very common: »
Changes being considered could open the floodgates and allow foreign markets to sell almost any stock to almost anyone in this country.
Main Entry: ↑floodgates
Financial and business terms. 2012.