Abstract:
Large errors in peak discharge estimates at catchment scales can be ascribed to errors in the estimation of
catchment response time. The time parameters most frequently used to express catchment response time are the time
of concentration (TC), lag time (TL) and time to peak (TP). This paper presents a review of the time parameter
estimation methods used internationally, with selected comparisons in medium and large catchments in the C5
secondary drainage region in South Africa. The comparison of different time parameter estimation methods with
recommended methods used in South Africa confirmed that the application of empirical methods, with no local
correction factors, beyond their original developmental regions, must be avoided. The TC is recognized as the most
frequently used time parameter, followed by TL. In acknowledging this, as well as the basic assumptions of the
approximations TL = 0.6TC and TC ≈ TP, along with the similarity between the definitions of the TP and the conceptual
TC, it was evident that the latter two time parameters should be further investigated to develop an alternative approach
to estimate representative response times that result in improved estimates of peak discharge at these catchment scales.
