The presented project being a part of rainfall-runoff modeling is focused on determination of relations between soil moisture changes detected in radar data and precipitations. One catchment area of– the Olse River in the northern Moravia is used for. The catchment's land cover classes derived from Thematic Mapper data are decisive for creation of homogenous land cover patches. The changes are determined from ERS-2 data. The radar data were chosen according to the flood precipitations date in the catchments covering either before and after flood period or only after a flood one. Radar image data processing is performed by following working steps: image data filtering, band subtraction, delineation and selection of the same land cover patches; these areas were subdivided according to their change values derived from the radar data subtraction. These subareas were evaluated in GIS to find relations between the spatial distribution of the radar data changes and hydrological, morphological, and soil conditions.