Nr. Bhaskar et al., FLOOD ESTIMATION FOR UNGAUGED CATCHMENTS USING THE GIUH, Journal of water resources planning and management, 123(4), 1997, pp. 228-238
Traditional techniques for design flood estimation use historical rain
fall-runoff data and unit hydrographs derived from them, Such procedur
es are questioned for their reliability due to the climatic and physic
al changes in the watershed and their application to ungauged areas. T
o overcome such difficulties, the use of physically based rainfall-run
off estimation methods such as the geomorphological instantaneous unit
hydrograph (GIUH) have evolved. In this study, the GIUH is derived fr
om watershed geomorphological characteristics and is then related to t
he parameters of the Nash instantaneous unit hydrograph (IUH) model fo
r deriving its complete shape. The model parameters of the GIUH and th
e Nash IUH model are derived using two different approaches. In the fi
rst approach (referred to as GIUH-I) the rainfall intensity during eac
h time interval is allowed to vary, whereas in the second approach (re
ferred to as GIUH-II) rainfall intensity is averaged over the entire s
torm period. This methodology has been applied to the Jira rivet subca
tchment in eastern India to simulate floods from 12 storm events. Resu
lts from both the GIUH approaches and those obtained by using Nash IUH
are comparable with observed events.