The study deals with flood estimation through computation of a flood hydrograph for the ungauged Narmada catchment upto Jamtara using the physical and geo-morphological characteristics of the catchment. The catchment area of 17100 sqkm has been sub-divided into five sub-catchments for the purpose of flood estimation.

The flood hydrograph for each sub-catchment has been computed using Geomorphological Instantaneous Unit Hydrograph (GIUH) method, which makes use of the physical characteristics of the sub-catchment. These computed flood hydrographs are routed through the respective river reaches to derive the final flood hydrograph at Jamtara.

Routing of flood hydrographs has been accomplished by using the Muskingum-Cunge routing method. The computed flood hydrograph is compared with the observed flood hydrograph at Jamtara. A total of five flood events were used in the analysis.

The geomorphological characteristics for a basin, other than the velocity were derived using a Geographical Information Systems (GIS) application of GIUH approach. Stream ordering and calculation of various geomorphological characteristics like number, length were done using GIS (ILWIS package).

The study demonstrates the use of methodology to compute floods, where the catchment size is large and very little or no information other than the rainfall is available.

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