Hydrodynamics and morphodynamics of shallow tidal channels and intertidal flats

In this thesis, mechanisms which control morphodynamics of shallow tidal embayments are investigated analytically. In the process of exploring these mechanisms (specifically asymmetries in bottom stress, Tau, basis momentum and mass balances which govern flow in these systems are clarified. Temporal asymmetries in Tau are investigated via a new perturbation scheme which quantifies nonlinear processes and combines geometric controls on asymmetry into a single non-dimensional parameter. Implications of spatial asymmetries in Tau are investigated through stability criteria based on a uniform distribution of Tau. Morphologic observations of both tidal channels and intertidal flats are consistent with a uniform distribution of Tau at equilibrium. Investigation of morphodynamic mechanisms leads to scalings of momentum and continuity which diverge from classical models. Scalings for prismatic channels with strong tidal asymmetries indicate friction often dominates acceleration in the momentum equation. The resulting zero-inertia balance gives a time-varying diffusion equation which requires along-channel amplitude to decay. Uniform Tau justifies a new scaling of continuity for exponentially-shaped channels. In such channels, along-channel gradients in tidal velocity are small and are often dominated by gradients in cross-sectional area. The resulting first-order wave equation allows only amplitude, forward propagating waveforms which are independent of channel length. Tidal channels Hydrodynamics, Tidal flats.