We derive a saturated sand flux model based on the previous models of Sauermann et al (2001Phys.Rev.E640313005) and Srensen (2004 Geomorphology5953) and determine its parameters, as a function of the grain and fluid properties, from a comparison with wind tunnel data. We also show that dunes simulated with the new sand transport model compare well with observations of Moroccan dunes. 2006 IOP Publishing Ltd and SISSA.