non-linear partial differential equations , called Boussinesq-type equations, which incorporate frequency dispersion (as opposite to the shallow water equations , which are not frequency-dispersive). In coastal engineering , Boussinesq-type equations are frequently used in computer models for the simulation of water waves in shallow seas and harbours . http://en.wikipedia.org/wiki/Boussinesq_approximation_%28water_waves%29 *** Deepwater Horizon