Flood Frequency Analysis of the Kaljani River of West Bengal: A Study in Fluvial Geomorphology

A floodFlood is defined as a relatively high flow or stage of a river, characterized by higher than normal, resulting in inundation of lowlands or water bodies, rising, swelling, and overflowing land that is not normally under water. Almost every year, floodsFlood hit the Kaljani River Basin with high magnitude. They put the people of the area in danger as they greatly affect the agricultural economy and infrastructure development of the area. The still unsolved floodFlood problem of Kaljani requires proper study and analysis of its peculiar flow patterns, especially aspects related to nature, frequency, probability, and magnitude of floodsFlood. In this context, the present chapter on flood frequency analysis is of great significance in mitigating the chronic flooding problem of the river. Flood frequency analysis involves interpreting the past record of flood events and predicting their future probability. Annual peak discharge data of Kaljani River at the Alipurduar district site for 23 years from 1985–2007 have been used for this purpose. Log Pearson Type-III Distribution method and Gumbel's extreme value distribution method have been used to test the probability of flood occurrence. The mean river floodFlood for Alipurduar is calculated at 606.42 m3 s−1 with a recurrence interval of 5.2 years by Log Pearson Type-III Distribution Method and 2.25 years by Gumbel's Extreme Value Distribution Method. Among flood frequency analysis methods, Gumbel's Extreme Value Distribution is considered to be more effective and suitable for estimating floodFlood occurrence probability and flood design for the Kaljani River.