Evaluating the Catastrophic Rainfall of 14 July 2016 in the Catchment Basin of the Urbanized Strzyza Stream in Gdańsk, Poland

Abstract

We analyzed the causes, the course, and consequences of the extreme precipitation events that occurred 14 July 2016 in the watershed of Strzyza Creek in Gdansk, Poland. Automated rain gauges located in Strzyza catchment registered a total precipitation lasting about 16 hours – from 129 to 160 mm of rain depth. More in-depth analysis based on rain data collected by Gdansk University of Technology (GUT) rain station was done. The course of rainfall was compared with existing rain models on the national range and also with local rain formula. The results showed that, according to the Chomicz classification, the rainfall can be qualified as torrential. Its course far exceeded the theoretical values calculated for the probability of occurrence 1% (return time: 100 years). Although the analyzed rain episode was characterized by extremely high instantaneous rainfall intensities, the duration of the most intensive middle stage of about eight hours caused the highest daily rain sum registered in Gdansk in the history of meteorological measurements. As a result, the rainfall caused two fatalities in the lower part of the Strzyza watershed. It was noted that this type of rain qualified as an extraordinary event at the turn of the XX and XXI centuries in areas located in the Mediterranean region. Rainfalls that currently occurr in this part of Europe are also characterized by proportionally higher parameters that should be considered as an indisputable effect of climate change on a global scale.