Lag time on torrential catchments in Serbia

Abstract

Maximal discharge Qmax(p) is the basic input data for designing longitudinal and transversal objects in torrential beds. Calculation of maximal discharge Qmax, on unstudied catchments, is carrying out by usage the theory of synthetic unit hidrograph and SCS methodology for separation effective rain Pe by total rainfall Pb. One of the basic time characteristics of torrential floods was analyzed: lag time tp. Lag time tp was determined on the basis of processing of hydrographs and deriving representative unit hydrographs, on 93 control profiles. Dominant physical-geography characteristics were determined: magnitude of the catchment area A, length of the catchment area along the main stream L, the distance from the centroid of the catchment area to the outlet profile Lc, average slope of the river bed Iu, average slope of terrain on the catchment area Isr. Lag time and dominant physical-geography characteristics were the basis for deriving some equations with regional significance (tp=f(L, Lc, Iu); tp=f(L, Lc, Iu, Isr)). The relation between lag time tp and time of concentration Tc was determined (tp=f(Tc)).