Page - 1149 - in Book of Full Papers - Symposium Hydro Engineering

Therefore, it is necessary to analyse any potential adverse effects of the changing (runoff) conditions on the relevant flood and erosion hazard of users of riparian and downstream space, as temporary conditions can negatively affect the spatial conditions even at high-waters with lower return periods. It was shown that the inclusion of hydraulic analysis into planning the stage-wise implementation is equally important as that in planning and optimising the final solutions of spatial developments. In the case of constructing structures and developments as part of HPP Brežice, the hydraulic calculations provided information about the appropriate planning of construction phases and identifying locations or dimensions of temporary structures and measures, as this provides an important retention area in the section between Krško and the state border and affects the runoff conditions in the border profile with the Republic of Croatia. Notably, NPP Krško is located in the impact area, where any deterioration of runoff and operational conditions is unacceptable, neither during the construction nor afterwards. By comparing intermediate situations and the results of the conditions prior to and upon completion of construction works it was necessary to determine and evaluate the potential deterioration in the individual phases of construction or changes in space, so that the HPP design engineer could predict different construction phases of the individual structures or propose and justify an additional set of (temporary) measures to remedy increased hazard and risk. This paper also underlines that users of space and activities that take place therein must be made familiar with the processes and impacts of step-wise construction, particularly during prolonged construction. We also recommend that with extensive spatial developments, along longer river section and with larger impact areas, periodic calculations of runoff conditions are carried out. Changes in space have a dispersed character, so it is necessary to check whether any changes or land use affect runoff to a degree when the conditions for siting a structure are no longer met. As in the past the conditions during high-water events have demonstrated, even changes in overgrowth in floodplain areas can significantly affect flows and change the level of flood hazard [9]. Such additional risks should be reduced as much as possible with an appropriate zoning resolution. 6. REFERENCES [1] RAK, G., STEINMAN, F. Considering the effects of human activities in flood hazard assessment. Proceedings of the 15th International Symposium Water Management and Hydraulics Engineering: 2-8, 2017. [2] MLAČNIK, J., RODIČ, P., NOVAK, G., VOŠNJAK, S., STEINMAN, F., RAK, G., ŠANTL, S., MÜLLER, M., CIUHA, D. Izvedba hibridnih hidravličnih modelov za območje spodnje vode HE Krško, območje HE Brežice in območje HE Mokrice, HHM za HE Brežice, Final report, Ljubljana, Inštitut za hidravlične raziskave, 2011. 1149