Flood Hydrograph Estimation Using Lumped and Distributed Models (Kabkian Basin Case Study)

Abstract

The mechanisms of rainfall and runoff were studied in the Kabkian basin (846.5 km2) in
Kohgilouye and Boyerahad, Iran.Since the hydrologic characteristics may change from one sub-basin to the
next, this analysis began by treating the Kabkian basin as a single entity. In this context, lumped models may be
referred to as "semi-distributed." HEC-HMS (Hydrologic Engineering Center, Hydrologic Modeling System)
and HEC-GeoHMS (Hydrologic Engineering Center, Geospatial Hydrologic Modeling Extension) are
hydrologic models. Models of rainfall and runoff were investigated, and in both situations the SCS curve number
approach (Soil conservation Service, 1972) was taken into account. Basin data was used to precisely calibrate
and verify the model. All flood episodes had determination and agreement coefficients more than 0.9, and the %
errors in peak flow and volume were within acceptable limits. The event model was then assessed using a locally
based sensitivity analysis. The sensitivity analysis focused on three factors of the event model: curve number,
initial abstraction, and lag time.There, in the Kabkian basin. The largest discrepancies between the produced
peak hydrographs and the baseline peak hydrograph were due to curve number in both the lumped and
distributed model. Semi- dispersed model performed better than Lumped model in capturing peak runoff
discharges and overall runoff volume. However, both models' overall performance was respectable.