The aim was to identify geographical areas of concern in the process of catchment delineation in urban areas in geographic information systems, GIS. The aim was also to develop a new method for the delineation in order to address identified problems. The calculations of the catchment areas are important for subsequent hydraulic modeling, which is performed in order to properly design storm water systems capable of handling the storm water. An object oriented method was developed that took into account the identified, problematic factors in the infrastructure and buildings of the urban area. An alternative algorithm for the preprocessing of the digital elevation model, DEM, was tested to see how the results would differ from a current method for catchment delineation with another algorithm for the preprocessing of the DEM. The two different algorithms for DEM preprocessing were used before the same procedure of catchment delineation was performed on the DEMs in ArcGIS. The delineated catchments from the two different preprocessing algorithms along with the object oriented method, were evaluated against reference catchment areas manually plotted by hydraulic modeling specialists. The object oriented method showed a higher correlation to the reference than the topographic methods for the most important target parameters when performing well. However the object oriented method has to improve in precision and efficiency if it is to be used for the calculations. The catchment delineation methods with different DEM preprocessing algorithms yields different results. For the DEM preprocessing, an algorithm from Whitebox GAT seemed to performed better in flat areas and in areas where the storm water lines have been lowered into the DEM, than the ArcGIS method did. However the combination of Whitebox GAT and ArcGIS resulted in some problems with the catchment delineation and hence the combined method has to be refined in order to be used.