In this study, with the aim of evaluation of effect of geomorphological landforms on flood properties, the GIUH theory has been investigated in Kangir (Eyvan) catchment. the geomorpholgical instantaneous unit hydrograph model, simulates and predicts the flood events for ungauged catchments by means of geomorphological characteristics. For testing the GIUH theory in Kangir watershed ,at first, quantitative geomorphological properties like bifurcation ratio (RB), area ratio (RA), length ratio(RL), length of highest order stream (L?) and then rainfall-runoff data and velocity- discharge equations were extracted and thereby QP (peak discharge) and TP (time to peak) were calculated for 5 storm events. The comparison of observed and estimated values represents that calculated QP values are, approximately, close to observed QP values. This study reveals that the performance of GIUH method in predicting QP values is relatively appropriate but it’s performance in predicting complete shape of hydrographs is inadequate. This study also reveals that geomorphological landforms such as karstic and tectonic holes and joints, decrease the runoff velocity and coefficient and therefore affect the QP and TP values. Also, complex relationships between karstic landforms and surface runoff and groundwater as well as rainfall characteristics, have resulted in low performance and lack of distinct trend of GIUH model in predicting flood. Result of this study shows that QP and TP values, also, are affected by variations of rainfall intensity in each storm event.
Keywords: Geomorphological instantaneous unit hydrograph (GIUH), Kangir, Peak discharge (QP), Time to peak (TP), Paths, RB, RL, RA.
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