Analysis of Annual Peak Flood Discharge Data by Log Pearson Type III Distribution of the River Krishnai of Assam

Abstract

The Krishnai river originates from the Garo Hills of Meghalaya at an elevation of about 280 meters above mean sea level. The catchment area of this river lies between 25° 35' to 26° 2' north latitude and 90° 20' to 90° 45' east longitude, in the Garo Hills of Meghalaya on the north slope of the state adjoining Assam. This paper offers an attempt to study the annual peak flood discharge data of the Krishnai river at the Velterghat gauging station using the Log Pearson Type III distribution model. Forty-six years of annual peak discharge data, collected from 1972 to 2018 from the Goalpara Investigation Division (Irrigation), Goalpara, are analyzed. The raw data are collected in cubic meters per second (m^3/sec) and arranged in descending order and ranked. The return period of the peak discharge of the Krishnai river at the Velterghat gauging station is calculated using the Weibull method, and the exceedance probability is calculated from the return periods. Finally, likely annual peak discharge values are estimated using the Log Pearson Type III distribution at the Velterghat gauging station of the Krishnai river. The analysis and results are helpful for policymakers when designing flood control measures in or near the Krishnai river.