It is found that basin hydrological response and model effective parameter identification in relations with the drainage basin dominating geomorphological parameters is directly influenced by the scale of DEM resolution. Thus a scale independent relationship in flood routing models is necessary for consistency in rainfall runoff translation at a scale of interest. To overcome this problem downscaling methods of dominating geomorphometric parameters are used to obtain the scale invariant distribution function of cross-section, depth, discharge and wave celerity from different DEM resolutions. The downscaling methods of the flow variables is then coupled with the Muskingum-Cunge routing method to develop a scale invariant routing model.