Description of regional approaches for the estimation of characteristic hydrological quantities

A. Efstratiadis, A. Koukouvinos, E. Michaelidi, E. Galiouna, K. Tzouka, A. D. Koussis, N. Mamassis, and D. Koutsoyiannis, Description of regional approaches for the estimation of characteristic hydrological quantities, DEUCALION – Assessment of flood flows in Greece under conditions of hydroclimatic variability: Development of physically-established conceptual-probabilistic framework and computational tools, Contractors: ETME: Peppas & Collaborators, Grafeio Mahera, Department of Water Resources and Environmental Engineering – National Technical University of Athens, National Observatory of Athens, 146 pages, September 2014.

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The objective of the report is the systematic investigation and evaluation of regional relationships and associated event-based models that are applied in flood studies, through validating their predictions across the pilot basins of the project. The research focuses on the most popular, in Greece as well as globally, hydrological design procedure, which is based on the application of the SCS-CN method for the estimation of hydrological losses, combined with the unit hydrograph theory for the transformation of surface runoff to flood hydrograph at the basin outlet. In the report are investigated both the theoretical-conceptual background of the models as well as the procedure for estimating their basic input quantities (time of concentration, runoff curve number, initial abstraction ratio, initial soil moisture conditions). In this respect, we analyzed more than 100 flood events in 11 sites of interest, which we attempted to represent through several alternative approaches. The analyses showed that it is essential to revise critical aspects of the hydrological design. The most important are: (a) the correction of the time of concentration, as estimated by the Giandotti formula, according to the rainfall intensity; (b) the estimation of parameter CN of the SCS-CN method on the basis of three characteristic layers of spatial information and its adjustment for given initial abstraction ratio; (c) the application of a parametric synthetic unit hydrograph, the time parameters of which depend not only on the characteristics of the basin’s surface but also the mechanisms of the shallow soil; and (d) the statistically consistent estimation of the flood design quantities on the basis of the probabilities of occurrence of the design rainfall under dry, medium or wet antecedent soil moisture conditions.

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Related project: DEUCALION – Assessment of flood flows in Greece under conditions of hydroclimatic variability: Development of physically-established conceptual-probabilistic framework and computational tools

Our works that reference this work:

1. E. Savvidou, A. Efstratiadis, A. D. Koussis, A. Koukouvinos, and D. Skarlatos, A curve number approach to formulate hydrological response units within distributed hydrological modelling, Hydrology and Earth System Sciences Discussions, doi:10.5194/hess-2016-627, 2016, (in review).

Tagged under: Floods, Hydrological models