Timing the time of concentration: shedding light on a paradox

E. Michailidi, S. Antoniadi, A. Koukouvinos, B. Bacchi, and A. Efstratiadis, Timing the time of concentration: shedding light on a paradox, Hydrological Sciences Journal, 63 (5), 721–740, doi:10.1080/02626667.2018.1450985, 2018.



From the origins of hydrology, the time of concentration, tc, has been conventionally tackled as constant quantity. However, theoretical proof and empirical evidence imply that tc exhibits significant variability against rainfall, making its definition and estimation a hydrological paradox. Adopting the assumptions of the Rational method and the kinematic approach, an effective procedure in a GIS environment for estimating the travel time across a catchment’s longest flow path is provided. By applying it in 30 Mediterranean basins, it is illustrated that tc is a negative power function of excess rainfall intensity. Regional formulas are established to infer its multiplier (unit time of concentration) and exponent from abstract geomorphological information, which are validated against observed data and theoretical literature outcomes. Besides offering a fast and easy solution to the paradox, we highlight the necessity for implementing the varying tc concept within hydrological modelling, signalling a major shift from current engineering practices.

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Our works referenced by this work:

1. A. Efstratiadis, A. D. Koussis, D. Koutsoyiannis, and N. Mamassis, Flood design recipes vs. reality: can predictions for ungauged basins be trusted?, Natural Hazards and Earth System Sciences, 14, 1417–1428, doi:10.5194/nhess-14-1417-2014, 2014.
2. S. Antoniadi, Investigation of the river basin's response time variability, Postgraduate Thesis, 124 pages, Department of Water Resources and Environmental Engineering – National Technical University of Athens, July 2016.

Our works that reference this work:

1. G. Papaioannou, A. Efstratiadis, L. Vasiliades, A. Loukas, S.M. Papalexiou, A. Koukouvinos, I. Tsoukalas, and P. Kossieris, An operational method for Floods Directive implementation in ungauged urban areas, Hydrology, 5 (2), 24, doi:10.3390/hydrology5020024, 2018.

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