Assessing the hydraulic performance of a combined sewer system under climate change using temporal downscaling
Abstract
In recent years, climate change has lead to an increasing number of high intensity rain events causing flooding in urban areas around the world. Studies of different future climate scenarios indicate that this increase will continue both in intensity and frequency. This study was carried out to create future IDF estimates for precipitation extremes in Trondheim, Norway, and to evaluate the hydraulic performance of the combined sewer system in Lerkendal drainage zone in Trondheim under climate change.
Temporal downscaling of spatially downscaled daily AM values from Global Circulation Models (GCMs) using the scaling concept and the Gumbel distribution was applied in the study. The hydraulic performance of the combined Sewer system was assessed using the modelling tool MIKE Urban.
The results from the downscaling, for the highest precipitation intensity increase, corresponded with using a climate factor of 1.4, which also is recommended by the Norwegian Centre for Climate Services to be used in dimensioning of drainage systems in the area. The results from the simulations indicated that the hydraulic capacity of the sewer system is insufficient, and that measures have to be done in the zone for adapting to the future climatic changes. The method applied in the study is easy to implement and would be beneficial for testing the performance of drainage systems under different climate change scenarios, to be a part of a risk analysis, and to inform decisions made in the planning and dimensioning of sewer systems.