Rainfall intensity variation for observed data and derived data-A case study of Imphal

For estimation of runoff especially for urban areas short duration rainfalls are necessary. However especially in developing countries like India availability of short duration rainfalls is scarce and data available is mostly for daily rainfall data. In such cases determination of design rainfall is becoming an approximation and thus leading to frequent failure of drainage network and subsequent floods. In the absence of short duration rainfall data[1], data is generated for short durations like 1hr, 2hr, 3-hr, 6-hr and 12-hr rainfall values were obtained using an Indian Meteorological Department (IMD) empirical reduction formula is used in the absence of observed data (t-hour rainfall). Frequency analysis was then carried out to establish Intensity-Duration-Frequency (IDF) relationships. In the present study an attempt has made to find the difference of intensity of rainfalls obtained from observed data and derived data by taking Imphal rainfall data whichis available for 15 min time interval.