This volume arises from an International Symposium on Flow and Transport in the Natural Environment held in Canberra, Australia, in September 1987. The meeting was hosted by the CSIRO Division of Environmental Mechanics (now the Centre for Environmental Mechanics) to mark the opening of the second stage of its headquarters, the F.C. Pye Field Environment Laboratory, twenty-one years after the opening of the first stage. Those twenty-one years have seen much progress in our understanding of the physics of the natural environment and the occasion provided an ideal opportunity to review advances in our knowledge of flow and transport phenomena, particularly with regard to flow and transport in soils, plants and the atmosphere. The contents of this volume are based very closely on the Symposium's program. Undoubtedly, our choices of topics were idiosyncratic, but we believe that those we have selected exhibit progress, innovation, and much scope for practical application. Rather than being encyclopaedic, we have sought to deal with thirteen selected topics in depth.