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

ABSTRACT

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.

KEYWORDS:

• design flood hydrograph
• characteristic flood hydrograph
• peak flow
• parametric hydrograph
• gamma distribution
• volume of flood

Editor A. Castellarin Guest editor C. Cudennec

Editor A. Castellarin Guest editor C. Cudennec

Acknowledgements

The work was carried out at the National University of Ireland (NUI) Galway at the behest of the Office of Public Works (OPW) of the Government of Ireland, as a component of the comprehensive FSU programme that the OPW undertook to develop improved methods for flood estimation in Ireland. The author gratefully acknowledges the sponsorship and support provided by the OPW, and its permission to disseminate knowledge created during this work. Special thanks are due to Dr Duncan Reed, the Technical Advisor, and the members of the Technical Steering Committee of the FSU programme, for their thorough reviews of and constructive suggestions on the work. The author expresses deep appreciation to Prof. Kieran M. O’Connor, Emeritus Professor at NUI Galway and supervisor of the OPW project on “Hydrograph width analysis” that the author worked on as the main researcher, and to Prof. Conleth Cunnane, then Head of the Department of Engineering Hydrology at NUI Galway and a member of the Technical Steering Committee of the FSU, for his support and encouragement. The author also thanks NUI Galway for administering the project related to this work and for its support.

Disclosure statement

No potential conflict of interest was reported by the author.