  This article reviews the main features of the transport properties of single
fractures. A particular attention paid to fractures in geological materials
which often display a roughness covering a broad range of length scales.
Because of the small distance separating the fracture walls, the surface
roughness is a key parameter influencing the structure of the void space.
Studies devoted to the characterization of the surface roughness are presented
as well as works aimed at characterizing the void space geometry. The
correlation of the free space is found to be crucially function of the failure
mechanism (brittle, quasi brittle or plastic...) but also of possible shear
displacements during the failure. The influence of the surface roughness on the
mechanical behavior of fractures under a normal load and a shear stress is also
described. Finally, experimental, numerical and theoretical works devoted to
the study of the influence of the fracture void geometry on the permeability
and on the hydrodynamic dispersion of a dissolved species are discussed.
