Statistical Approaches for Regionalisation and Interpolation of Intense Precipitation for Climate Resilience in South Tyrol

Abstract

Reliable design storms are indispensable for climate-resilient drainage in the Alpine province of South Tyrol, where steep orography produces sub-kilometre rainfall contrasts that existing atlases fail to capture. The present study proposes a comprehensive methodology for interpolating intense precipitation data in South Tyrol. Utilising advanced statistical techniques, including exponential distribution and Ordinary Kriging interpolation, the study offers a reproducible workflow that converts 5-minute gauge records from several stations in South Tyrol into a 1 x 1 km grid of Intensity-Duration- Frequency (IDF) curves. The objective of the study was to enhance hydrological modelling and flood risk assessment across various durations and return periods. After rigorous quality control, the annual maxima are fitted with the exponential distribution and the scale (u) and slope (w) parameters are then regionalised by 3D ordinary kriging within six homogeneous subregions. The approach was validated against observed station data, thereby confirming its robustness. The novel grid has demonstrated efficacy in reducing interpolation error whilst concomitantly enhancing the resolution of the valley-ridge gradient characteristic of convective Alpine storms. The released dataset provides the first kilometre-scale basis for urban drainage design, flood mapping and climate adaptation planning in South Tyrol and offers a transferable framework for other mountain regions.