The design flood under two approaches: synthetic storm hyetograph and observed storm hyetograph

Abstract

This paper evaluates the design peak flow for several return periods using two approaches: 1) a flood frequency analysis; 2) rainfall-runoff model applied to a design storm. The design storm originates from the design rainfall depth, which is distributed throughout the rainfall duration via synthetic hyetographs. In the flood frequency analysis, the design peak flow was obtained from a 30-year series of flows estimated from rainfall observations at a five-minute time step. The design storm was routed with the same rainfall-runoff model and parameters to yield the design peak flow. The hyetographs tested were categorized as having advanced, delayed, alternating, uniform and empirical blocks that were built from rainfall observations. All design storms analysed undersized the hydraulic structures. The results, which were valid for the study region, indicated the need to rethink the concept of design storms, which associate the design storm depth with synthetic hyetographs, for a conservative standard.

KEYWORDS:

• Design flood
• design storm
• syntheti hyetographs
• HEC-HMS

Acknowledgements

We would like to extend our gratitude to CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for the scholarship provided and Campus de Pici at the UFC (Universidade Federal do Ceará) for the meteorological data provided for this case study.

Additional information

Notes on contributors

Catine António Chimene

Catine António Chimene, Former researcher and lecturer at the higher School of Rural Development (Escola Superior de Desenvolvimento Rural), Eduardo Mondlane University (UEM). He is currently a Ph.D student enrolled in 2015 (on going) at the Universidade Federal do Ceará, Departamento de Engenharia Hidráulica e Ambiental, Fortaleza – Ceará, Brazil. He accomplished his MSc degree in Municipal Water Infrastructure, Water Supply Engineering at the UNESCO-IHE, Delft in the Netherlands.

José Nilson B. Campos

José Nilson Campos, Graduated in Civil Engineer and MSc degree holder in water resources management from the Federal University of Ceará. Obtained his Ph.D. in Water Resources Management at the Colorado State University in 1987. He worked as an Engineer at the National Department of Drought Works (DNOCS) until 1989 where he elaborated many hydrological studies. He is actually retired professor but he is still collaborating with the post-graduate process by teaching and research. He was Head of the Brazilian Association of Water Resources for the 2003-2005 biennium. Deputy Dean of the Engineering I at Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) in the 2007-2010 triennium. He works mainly in the following subjects: planning and management of water resources, climate studies and hydrological regime of the Semiarid, climatic variability. He outlined hydrological studies of more than 50 reservoirs in the Northeast of Brazil. He has been a member of the Dams Safety Panel in Northeast Brazil since 1996. He is the author of a reservoir design methodology applied in the Northeast since 1992. He has 50 papers published in refereed journals and more than 100 complete articles published in annals of national and international events. He is a peer-reviewed of Elsevier's Journal of Hydrology and Springer's Water Resources Management Journal. He is editor of the Sanitary and Environmental Engineering Journal. He is a member of the Brazilian Commission together with the International Hydrological Program because of his knowledge in the semiarid theme.