Estimation of catchment response time using a new automated event-based approach
Eszter Nagy, József Szilágyi, Péter Torma
Abstract
The estimation of catchment response time (Tr) plays an important role in several hydrological and civil engineering design problems. The non-linear relationship between Tr and rainfall intensity necessitates the estimation of an event-based set of Tr values instead of a characteristic constant value. However, there is no generally accepted method to define individual rainfall-runoff events from time-series. Here we propose a new, automated method which results in the selection of rainfall-runoff events and the corresponding Tr values. The proposed method yields an event-based set of Tr values more efficiently than other existing methods and has only two parameters. The results of the new method were compared to those of a statistical and a semi-manual event selection approach. The latter calculates eight different Tr values, including the time of concentration, lag time, time to peak, and time to equilibrium. The median Tr value of the proposed method yields the strongest agreement with the median of the time elapsed between the maxima of the total rainfall and runoff with a root-mean-square error of 4.94 h. It is also demonstrated that a median time of concentration value can be estimated as the maximum of the event based Tr values by the current method. A sensitivity analysis explores the robustness of the proposed method, and also yields the optima of its two parameters. Once calibrated, the present automated methodology dispenses with any event selection procedure.