The intensification of short-duration rainfall extremes due to climate change – Need for a frequent update of intensity–duration–frequency curves

Abstract

Numerous studies have investigated future changes in extreme precipitation by employing climate models. However, trends in extreme short-duration (20–180 min) rainfall intensities, that is, design storm rainfall intensities used for stormwater infrastructure design, have received considerably less attention despite their importance. This study quantified the effect of climate change on design storm intensity based on observations. Trends were investigated for diverse short-term rainfall durations, ranging from 20 to 180 min, at 11 meteorological stations in Northern Europe, Estonia. The Mann-Kendall test and Sen's slope estimator were used to detect trends and calculate the trend magnitudes by analyzing a 70 year period of high-resolution temporal observed rainfall data. The Sen's slope indicated a positive magnitude of slopes for all the durations and stations investigated, and two stations in Northeast Estonia showed significantly increasing trends (p < 0.05). Unsurprisingly, the spatial distribution of trends revealed notable variations from station to station, as extreme rainfall events are heavily localized due to cloudburst. Despite this variety, it can be generalized that the annual maximum rainfall intensities in Estonia have increased at an average rate of 4 % per decade due to changing climate conditions, invariant of the rainfall duration analyzed. The use of decades enables to easily keep the intensity–duration–frequency curves updated, and it is more practical and relatable for engineers as well. The findings of this study provide critical knowledge for urban water management decision-makers, indicating the need to frequently update urban design criteria to design climate resilient urban infrastructure.