The TRU-FLAP Floating Flap System is designed to prevent flooding and backflows caused by high downstream water levels and acts as a floating weir whose crest elevation self-adjusts. The TRU-FLAP can and has been installed at combined sewer overflow (CSO) locations, sanitary sewer overflow (SSO) locations, retention tank overflows and basin overflows. Overloading of sewer systems and sewage treatment plants is avoided and energy costs for pumping systems and sewage treatment are reduced.