Analysis of observations



To corroborate the following hypotheses:

  1. Fortnightly switching in the residual flow direction differs with the along-estuary distribution of the density field.
  2. The internal tidal Froude number (Fr0, see below)) will change along the estuary and diagnose the main flow drivers (see below).


Expected results
  • Distinct structure of residual flows across the channel on neap and spring tides.
  • Fortnightly variability of the subtidal structures along the estuary.
  • Along-estuary density gradients.
  • Applicability of Fr0 as a diagnostic for hydrodynamic switching.


Internal tidal Froude number Fr0:

The internal tidal Froude number, Fr0, compares the tidal stress to the baroclinic pressure gradient. It is defined from the tidally-averaged momentum equation:

Fr02 = V02 / (g’H )

where V0 is the along estuary tidal current amplitude (in m/s), g’ is the reduced gravity (m/s2) and H is the water depth (m).