Abstract: Tide gates are frequently placed at confluences of streams with tidal waters. These gates prevent tidal waters from inundating low-lying lands while allowing stream flows to drain during lower tidal stages. Traditional tide gates effectively preclude an estuarine environment upstream of the gate and often block native fish from entering these tributary streams. In recent years, a new generation of tide gates has been installed with the intent of improving fish passage and allowing a limited amount of tidal inflow into the stream to create a longitudinal transition from the marine to freshwater environment. This new generation of tide gate uses side-hinged doors that open wider to permit efficient outflow and produce slower water velocities to accommodate fish passage. These gates also allow a limited amount of tidal water to flow upstream. Inflow of tidal water is regulated to mute the peak tidal stage and preventing upstream tidal flooding. The muted tide is regulated by either: 1.a small adjustable opening that functions as an orifice and sized to prevent excessive tidal inflow, or 2.a mechanical float system that holds the gate open until the upstream stage reaches a predetermined threshold. Design of these muted tidal systems involves extensive hydraulic analysis to evaluate fish passage, prevent upstream tidal flooding, and create the desired estuarine conditions, including vegetation zonation. This presentation will illustrate the types of analysis and considerations employed with this new generation of tide gates. Two recently constructed tide gate replacements designed for passage of all life stages of Pacific anadromous salmonids will be used as case examples to highlight the design process