Abstract
ABSTRACT The Unit Hydrograph (UH) is the most popular method for flood related applications. There are several conceptual and geomorphological models based on UH and coupled with different spatial discretizations. However, there are few studies concerning the evaluation of UH models according to semi-distributed approaches. This study aimed to assess the influence of lumped and semi-distributed modeling on the applicability of Soil Conservation Service UH (SCS UH) and Clark’s Instantaneous UH (Clark’s IUH) for estimation of flood hydrographs. The methodological procedures were conducted in the Hydrological Modeling System (HEC-HMS) using rainfall-runoff events of a gauged watershed in Southern Brazil. The main conclusions were: a) CIUH under the semi-distributed approach provided slightly superior performance; b) CIUH was able to effectively estimate the direct surface runoff hydrographs even for long duration rainfall events; c) SCS UH presented more accurate hydrographs for lumped modeling; d) the Nelder and Mead algorithm may have limited application.
Highlights
Natural disasters have been mainly related to population growth, occupation of risk areas and climate change effects on hydrological cycle
Considering the two adopted scenarios, curve number (CN) was determined for each rainfall-runoff event according to two procedures: (i) scenario 1 – CN value was calculated such that the sum of all Pes over time would be quantitatively equal to the observed direct surface runoff (DSR), which was derived from information resulting from the automatic monitoring station located at the outlet; (ii) scenario 2 - CN was calibrated in Hydrologic Engineering Center (HEC)-HMS for each sub-watershed
Considering assessments associated with flood modeling, rainfall events with variable amounts have been used for analyses performed by various researchers over the world (GONZALO; ROBREDO; MINTEGUI, 2012; SADEGHI; MOSTAFAZADEH; SADODDIN, 2015; GHORBANI et al, 2017)
Summary
Natural disasters have been mainly related to population growth, occupation of risk areas and climate change effects on hydrological cycle. Flood is one of the most common types (BRUNDA; NYAMATHI, 2015), which is influenced by extreme rainfall events. The success of both flood management implementation and its mitigation in watersheds depends on the awareness of runoff in water courses, especially in terms of their water levels and streamflows (HAO et al, 2015). When the watershed flood analysis is conducted based on limited data sets, the choice for a model and its parameters become an important step for direct surface runoff (DSR) estimation (AHMAD et al, 2010). Unit hydrograph (UH) is the most usual method to estimate DSR hydrographs, besides being widely used, primarily in developing countries (GHORBANI et al, 2017)
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