To simulate the response of the sewer system on the changes, data and models are coupled with the established hydrodynamic model SWMM (Gironás et al. 2010). As indicators for the sewer system performance changes in flooding volume and combined sewer overflow volume have been chosen.
Methods
To assess the performance of the sewer system the data provided by the previous work packages was used in a hydrodynamic model of the drainage network of the city of Innsbruck. To further be able to assess possible adaptation measures three version of the model have been used. One originating from 2005 (Möderl 2009), a second an extended version of this model, the other one generated during this project with data provided by the Page 13 / 39ACRP – Calls for Proposals local operating company (IKB). This give the possibility to analyse the effects of roughly 10 years of network change and adaptation. Especially the comparison of the old and new network under the influence of possible future conditions can give an interesting insight on adaptation measures.
The performance of the system is assessed by means of ponded (flooding) volume leaving the system and CSO discharge. These overall performance indicators were chosen because they can be used the express system-wide performance. In addition to the purely 1D model of the sewer network a 1D-2D model of the inner city has been created. The purpose of such a model is to get detailed information about flooding events in urban areas. Not only in terms of volume leaving the sewer system, but information about flood paths and depth and is necessary to assess the risk of flooding for buildings and other structures. At the same time this increases the difficulty in creating the model and computational time.
In total about 100.000 hydrodynamic simulations have been processed. The configuration of the variations can be examined in Table 3. Apart from the listed variations, numerous simulations outside the standard scheme have been done, e.g. with long term rainfall files and parking lots used as retention volumes.
Results
Below the ratio in relation to the base network, base year and without climate change influences is visualised. On the x-Axis the flooding volume, on the y-Axis the CSO volume, the colour varies with climate – emission scenario, shape with development year. As can be seen there are significant differences in CSO volume and flooding volume between different climate–emission scenarios and as expected with not as significant differences for the original data without a climate factor, as well as E5-A1B.
Ratio of flood volume and CSO volume in relation to the base scenario for all simulations