The survey work of flood affected area of river basin is significant factor in flood management. The floodmanagement work is done by analysing water discharge and water profiles at different cross-sections of river basin. Riverbed plays crucial role in distribution of flood water and water velocity profile. Hence topographical detailed survey is verymuch essential for flood management works.Traditionally topographical survey work is carried out manually by using total station to acquire detailed data on theactual spot by the people on the ground. On the other hand, in aerial surveying UAV borne mapping system is developedfor survey purpose of river basin in which digital and infrared cameras are used along with GPS. This paper focuses oncomparative study between conventional topographical survey and drone or aerial photographic survey by using the HECRASsoftware for achieving results. The comparison is done on the basis of flow rate, water depth and velocity across theflood plain of river. The evaluated parameters in the study provides a guideline for the decision making process for waterresource management projects