Abstract:  Using simple models and observations, I will discuss the fluid mechanics
of wave driven flow over coral reefs. In particular, I will present results
of observations made on the north shore of Moorea that illustrate several
important features of how these flow work: (1) Stokes drift, the net
transport due to oscillatory motions of the waves, plays a significant
role in the net flow over the forereef; (2) The radiation stress model
used to analyze longshore flows on beaches works reasonably well for
predicting the setup of the free surface that drives flow inshore of
the surfzone; and (3) the waves themselves are quite nonlinear on the
shallow forereef immediately offshore of the surf zone, although key
quantities like radiation stress and Stokes drift can be predicted with
reasonable accuracy using the free-surface variance (rather than simple
wave height) without knowing the profile of the waves themselves.  In
addition to these observations I will discuss a simple 1D model of this
flow that shows how reef slope and backreef roughness and length can be
important to water level setup and flow over the reef.

Host:  Eckart Meiburg