S. De Toffol

Are extreme rainfall intensities more frequent? Analysis of trends in rainfall patterns relevant to urban drainage systems.

The fact that climate change is affecting the intensity and frequency of rainfall is well accepted in the scientific community. This is backed by a multitude of reports on the basis of daily rainfall series analysis; however, little research is available for short duration intensities. Due to its significant influence on the behaviour of urban drainage, it is critical to investigate the changes in short duration rainfall intensities. In this study different intensities relevant for the urban drainage and the total rainfall per rain event are analysed. The trend is investigated using the Mann-Kendall test. The rainfall series analysed are from the alpine region Tyrol. The results present differences depending on the duration of the intensity and the series considered, however an increase in the number of extreme events is detectable for short durations for the most series.

Suitability of CSO performance indicators for compliance with ambient water quality targets

The aim of the present paper is to assess the applicability of easily obtainable emission-based performance indicators for combined sewer overflows in order to describe the water quality in the receiving water. Theresultsof the computer simulations showed a correlation of some emission-based indicators with discharged loads. However, none of the emission-based indicators was correlated to acute effects. Owing to the correlation of the total overflow volume with the impacts in the receiving water, the outcomes of this study suggest thatreceiving waters in regions with a high annual rain volume are more endangered by combined sewer overflows.