Seite - 1144 - in Book of Full Papers - Symposium Hydro Engineering

Fig. 7: Comparison of the velocity field and depths for the condition prior to the construction and the final location and shape of the disposal site for the material excavated from the construction pit and the diversion channel at a 100-year return period event. In terms of costs and flood safety the relocation of the disposal sites upstream from the construction pit would be more suitable, where the cross-section of the right retention (floodplain) is large enough while the impact of the disposal sites would be smaller. Nevertheless this was not possible due to the archaeological site, where the investigations were conducted throughout most of the HPP construction. For other disposal sites on the right bank of the Sava the calculations showed that the critical point in constructing the weir and levees occurs at the narrowing between the construction pit and the Ljubljana–Zagreb motorway, therefore the only option was to remove the disposal sites as far as possible from the Sava River to the left bank of the Krka River. Figure 7 shows the final shape of the disposal site for the total quantity of the material dredged from the diversion channel. The shape is adapted according to the streamlines in the right inundation at the construction pit. In this way, the disposal site in the corner between the left bank of the Krka River and the motorway embankment would temporarily function as a levee to avert the intrusion of the water from the Sava River into the Krka. This would already in the construction phase decrease the flood hazard of the settlements along the Krka River, as was demonstrated in a previous study [4] about levees along the left bank of the Krka River. In the case of a high-water event during the Brežice HPP construction the water level of the Krka River below the motorway bridge would decrease by up to 50 cm relative to the situation prior to the construction. Figure 8 shows the conditions in 2014, at the Sava River discharge of approx. 2000 m3/s. 1144