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