Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Hydrol. Earth Syst. Sci., 22, 943-956, 2018
https://doi.org/10.5194/hess-22-943-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 Feb 2018
A dimensionless approach for the runoff peak assessment: effects of the rainfall event structure
Ilaria Gnecco, Anna Palla, and Paolo La Barbera Department of Civil, Chemical and Environmental Engineering, University of Genova, Genoa, 16145, Italy
Abstract. The present paper proposes a dimensionless analytical framework to investigate the impact of the rainfall event structure on the hydrograph peak. To this end a methodology to describe the rainfall event structure is proposed based on the similarity with the depth–duration–frequency (DDF) curves. The rainfall input consists of a constant hyetograph where all the possible outcomes in the sample space of the rainfall structures can be condensed. Soil abstractions are modelled using the Soil Conservation Service method and the instantaneous unit hydrograph theory is undertaken to determine the dimensionless form of the hydrograph; the two-parameter gamma distribution is selected to test the proposed methodology. The dimensionless approach is introduced in order to implement the analytical framework to any study case (i.e. natural catchment) for which the model assumptions are valid (i.e. linear causative and time-invariant system). A set of analytical expressions are derived in the case of a constant-intensity hyetograph to assess the maximum runoff peak with respect to a given rainfall event structure irrespective of the specific catchment (such as the return period associated with the reference rainfall event). Looking at the results, the curve of the maximum values of the runoff peak reveals a local minimum point corresponding to the design hyetograph derived according to the statistical DDF curve. A specific catchment application is discussed in order to point out the dimensionless procedure implications and to provide some numerical examples of the rainfall structures with respect to observed rainfall events; finally their effects on the hydrograph peak are examined.

Citation: Gnecco, I., Palla, A., and La Barbera, P.: A dimensionless approach for the runoff peak assessment: effects of the rainfall event structure, Hydrol. Earth Syst. Sci., 22, 943-956, https://doi.org/10.5194/hess-22-943-2018, 2018.
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Short summary
The paper proposes a dimensionless framework to investigate the impact of the rainfall event structure on the runoff peak. A set of analytical expressions are derived from a constant hyetograph to assess the maximum runoff peak for a given event structure irrespective of the specific catchment. A catchment application is discussed to point out the dimensionless procedure implications and to provide some numerical examples of the rainfall structures with respect to observed rainfall events.
The paper proposes a dimensionless framework to investigate the impact of the rainfall event...
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