Applicability of geomorphological approaches combined with the modified Clark’s model for flood hydrograph estimation

Abstract

Among the techniques available for modeling direct surface runoff (DSR), the Unit Hydrograph and the Instantaneous Unit Hydrograph (IUH) have been widely used. Clark's IUH (CIUH) stands out, mainly in its distributed version known as ModClark, which has two parameters: time of concentration (tc) and storage coefficient (R). The best procedure is to determine tc and R from observed rainfall-runoff datasets, however, they usually are not available due to a lack of monitoring or insufficient temporal discretization. Thus, geomorphological approaches have been developed to allow the estimation of tc and R from relief information of the watershed, however, their use is little disseminated in literature. In addition, only a few studies have evaluated the influence of spatial discretization of the watershed on the definition of tc and R (parameterization) and its impact on the application of geomorphological approaches for the ModClark. This work aimed to evaluate the ModClark performance for estimating DSR hydrographs in two Brazilians watersheds (Cadeia river watershed and Jaguara creek watershed), using four little-known geomorphological approaches (PST, POA, PD, and PMC) for the determination of its parameters under two parameterization schemes: lumped and semi-distributed. The following findings were evidenced: i) the application of the ModClark presented a satisfactory performance for estimating DSR hydrographs; ii) the characteristics of the selected rainfall-runoff events also had a significant influence on the estimation of the DSR hydrographs; iii) the lumped parameterization scheme provided more adequate parameters for ModClark, thus resulting in more accurate DSR hydrographs; iv) PST gave the most accurate estimated DSR hydrographs for the Cadeia river watershed under both schemes and for the Jaguara creek watershed under the lumped scheme, whereas PMC outperformed the other approaches for Jaguara creek watershed under semi-distributed; and v) for watersheds with geomorphological characteristics similar to those of the watersheds analyzed in this study, PST would be the most suitable geomorphological approach for determining the ModClark’s parameters.