Hillslope hydrological modeling and runoff modeling in small catchments is considered to be of great importance for the understanding and quantification of hydro ecological processes in mountainous landscapes: In the recent year a number of new ideas and models were proposed at the hillslope scale. In the paper an overview of the evolution of runoff generation theories and mechanisms on hillslopes and in small catchments is presented together with a brief review of the main mathematical modeling concepts used in small catchments. The limitations of these theories for engineering hydrology are discussed and an iterative concept for catchments-modeling using distributed models is suggested. The presented model performs a reasonably detailed calculation of Hortonian surface runoff combined with a simpler conceptualization of subsurface processes in order to avoid the complications with data collection on soil and subsoil characteristics.