The article introduces a kind of flip-flap dam (in the form of a self-turning valve door) the lower axis works according to the principle of automatically balancing the collapsing force to raise water and remove flood. This is a new research result when combining hydrodynamics and mechanical engineering. With the use of a spring system to create the anti-roll torque, it is possible to meet different water levels when using a spring of equivalent hardness, this is the main advantage of this type of valve. This type of valve door can be made available for each unit so it is easy to transport, install and replace.