Long‐term Trends in Extreme Precipitation Indices over Cachar District of Assam : 1901-2021

Abstract

This study investigates long-term trends in extreme precipitation indices over Cachar district, Assam, from 1901 to 2021, focusing on their spatial and temporal variations and implications for urban flood management. Using gridded rainfall data and indices defined by the Expert Team on Climate Change Detection and Indices (ETCCDI), the analysis reveals significant changes in precipitation patterns, including increases in very heavy rainfall (R50mm) during annual, monsoon, and pre-monsoon periods. Conversely, moderate (R10) and heavy (R20) rainfall frequencies show a declining trend, while daily precipitation intensity (SDII) has increased, particularly in pre-monsoon seasons. The study employs the Modified Mann–Kendall (MMK) test at a 95\% confidence level and Sen's slope estimator for trend analysis, highlighting an increasing trend in extreme events like R1day and a significant reduction in consecutive wet days (CWD). These findings underscore the need for improved urban flood mitigation strategies, especially as intense precipitation events become more frequent in Cachar district. This work provides critical insights into the impact of climate variability on hydrological systems, emphasizing the role of sustainable urban planning in addressing future climate challenges.