MEAN ANNUAL FLOOD ESTIMATION

A dimensional analysis approach to a regional analysis of annual flood peaks in much of India is described and developed. Dimensional variab les were formed using the mean annual flood, the average rainfall, the rainfall duration, the return period, the drainage area, the catchmen t slope, the fraction forested, and the gravitational acceleration. Th e utility of the approach is demonstrated by fitting it to a sample of 93 Indian catchments (river basins) ranging in size from 14.5 km(2) t o 935,000 km(2), and with record lengths of 10 to 84 years. Most (90%) of the model predictions fall within +/-50% of the observed mean annu al flood. During the calibration of the model, average rainfall of dif ferent durations varying from 0.75 h to 12 h and return period varying from 2 to 25 years were used. The validity of this model was further investigated using the average rainfall of 24 h duration and 2 yr recu rrence interval. Although the model was validated with only a 2-yr-ret urn-period 24-h-duration rainfall data, it was found that 85% of the m odel predictions fell within +/-50% of the observed mean annual flood.