This paper reviews some of the most basic flows that effect the dispersal of heat and mass in environmental configurations. Two important classes of environmental flows are discussed: free turbulent flows (shear layers, jets, plumes and wakes) and free flows in porous media (plumes, wakes behind concentrated sources of heat and mass, plumes, penetrative convection). These flows are 'free' from the effect of confining boundaries. The emphasis is on fundamental mechanisms and the methods (use the simplest first) that have been developed for the prediction and description of environmental flows. Copyright (C) 2003 John Wiley Sons, Ltd.