Analysis of 38 rainfall-runoff events, recorded in a small urban catchment (A = 28.7 km²), located in south-west part of Warsaw, in the period of 2009–2012, has been carried out with the aim of estimating the lag times, and checking they variability. The lag times of recorded events were compared with the estimated ones from empirical formulae. Results of analysis indicated significant variability in lag times among the events (since 1.77 to 15.8 h). Relations between lag time and event characteristics used in selected formulae were not confirmed by the recorded data.

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