The paper submitted is the third one of the series of studies dealing with evaluation of spatial categories of shape and size in the landscape ecological planning (LANDEP) method (Ruzicka, Miklos, 1982). In this paper we present an applied procedure of evaluation of the size of elementary surfaces from the aspects of the surface run-off, as well as evaluation of branching of hydrographic systems into microbasins from the point of view of gradual integration of the runoff in a basin. As an example we present the possibility of application of these methods to the solution of selected hydrologic problems of a territory of the East Slovakian Lowland. -Authors