Generating design flood hydrographs by parameterizing the characteristic flood hydrograph at a site using only flow data

A paucity of precipitation data often precludes the application of traditional unit hydrograph and synthetic unit hydrograph methods for generating the design flood hydrograph (DFH) at a catchment outlet. However, flow data, either recorded or derived by deterministic approaches, are readily obtained for many catchments. In this paper, analytical methods for generating a DFH having its peak matching the peak flow of a specified return period, or a flood hydrograph beneath a known peak flow at a site, are presented. Only flow data in the case of a gauged site, and flow data together with data of physical descriptors of catchments at gauged sites in the vicinity in the case of an ungauged site, are used to develop a parametric semi-dimensionless characteristic flood hydrograph (CFH); finally, the CFH, which also enables volume estimation, is scaled up for fleshing out a DFH beneath a specified peak flow at that site.