For the description of the surface condition of components of structures the absolute hydraulic roughness in hydraulic engineering and the geometrical roughness in the material science are normally used. Definite coherences between these parameters could not be found yet up to now. A method to determine the surface roughness of concrete structures has been developed at the Institute of Hydraulic Engineering and Technical Hydromechanics of the TU Dresden (IWD). Furthermore it is quite obvious that the hydroabrasion process of concrete surfaces causes erosion and leads to an increase of the hydraulic and geometrical roughness. The maximum grain size of the concrete matrix mostly influences this effect. By using fine concrete shutterings the hydraulic roughness can be nearly equated with the geometrical one. The roughness relations of concrete surfaces effected by hydroabrasion are analysed yet.