Generation of Intensity–Duration–Frequency Curve for Tezpur, Assam

Abstract

Calculating rainfall intensity–duration–frequency curve (IDF curve) is a pre-requisite in water resource engineering for the development, management and planning of hydraulic infrastructures such as barrages, spillways and for various engineering projects against design floods. The objective of this study is to develop an IDF curve relationship for Tezpur, Assam for a short duration of 15 years which will be helpful for the design of drainage work like storm sewers, culverts, etc. In this study, the rainfall data of 15 years, i.e., from 2007 to 2021 has been collected from the Water Resource Department of Tezpur. Firstly, the peak annual daily rainfall was found out and then, Gumbel, log-normal and normal distributions have been used to calculate probable maximum rainfall intensity for a return period of 2, 10, 25, 50, 75 and 100 years from the maximum annual rainfall. The other objective of this study is to compare the IDF curves derive from these three distributions and is to find the best IDF curve for Tezpur. For Gumbel’s analysis, the value of reduced mean and reduced standard deviation has been taken as 0.5128 and 1.0206, respectively, for 15 numbers of sample sizes. The data trend illustrates that as duration increases, the intensity value declines and that rainfall increases with length for a particular duration as return period increases, intensity tends to increase. It is also observed that log-normal distribution gives the lowest variation for different return periods. The derived IDF curve model can be further used for flood forecasting.