Effects of constructing feasible detention dams in urban basins, immediately upstream an urban area, were studied. Comparisons were made between this practice and conventional localized river engineering countermeasures regarding socio-economic aspects. For assesment of the effects of detentions dams, 3 scenarios were tested. To evaluate the scenarios, ARCVIEW GIS with GEO-HMS extension, linked with HEC-HMS as mathematical model were used. The study was conducted in an urban basin in south of IRAN. Upon determination of design flood, the effects of flood magnitude on conveyance canal dimensions, with and without detention dams, were compared. Total costs of both flood control alternatives were estimated and compared. Results showed that incorporation of detention dams in urban basins for flood control purposes was superior to conventional localized Urbam Basin, localized river engineering.