Tidal Hydraulics in Estuarine Channels

Alternating hydraulic flow (typical of estuarine areas) cannot be accurately treated using techniques developed for open channels or for the open oceans. As tidal energy approaches our coastlines, the potential energy is converted to kinetic energy resulting in forced vibrations within our estuarine systems. These hydraulical vibrations are periodic rather than truly harmonic but can be considered to be harmonic for a first-order approximation. By making the analogy to electrical alternating current flow with a quadratic resistance term, the equation of motion of tidal channel flow can be written. Solution of this harmonic equation in simplified form leads to expressions for channel resistance, channel capacitance, and channel inductance which combine, according to the phase angle between tidal amplitude and tidal current, to form channel impedance. These equations reduce to the familiar Darcy-Weisbach equation for steady-state open channel flow.