Abstract:
Intensity-Duration-Frequency (IDF) curve is an essential hydrologic tool used for
the design of hydraulic infrastructure. In a changing climate scenario, the assumption of a static
return period of precipitation extremes is not valid; the under-estimation of rainfall intensity
values may lead to the failure of critical infrastructure. This paper is focused on identifying the
extent of non-stationary behaviour at different locations in Kerala. The annual maxima rainfall
data prepared from daily time series was idealized into non-stationary Generalized Extreme
Value (GEV) distributions, with time-varying parameters after rainfall disaggregation
operation. Non-stationary rainfall intensities were estimated using different non-stationary
models, and the best model was identified using Akaike Information Criteria (AIC). From the
analysis using station-wise data, it was found that districts including Palakkad, Malappuram,
Idukki and Pathanamthitta were experiencing significant non-stationarity in extreme
precipitation events. Non-stationary rainfall extremes were concentrated at Eastern regions of
Kerala compared to coastal and midlands of Kerala.
