Page - 1136 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- HYDRAULIC ANALYSIS OF TEMPORARY FLOOD HAZARD TO SUPPORT THE PLANNING OF THE CONSTRUCTION PHASES OF HYDROPOWER PLANTS Gašper RAK, Franci STEINMAN Chair of Fluid Mechanics with Laboratory, Faculty for Civil and Geodetic engineering, UNIVERSITY IN LJUBLJANA, SLOVENIA SLOVENIA 1. INTRODUCTION With any major spatial developments (construction projects) it is necessary to analyse both anthropogenic environmental impacts as well as the impact of the environment on the planned structure [1]. One of the technical basis in environmental impact assessment concerning developments in and near rivers and in their impact zone is to analyse the runoff regime, which indicates the difference between the existing and the planned state of water flows, depths, velocities, erosion, etc. Physical and mathematical hydraulic modelling is a commonly established practice to ensure that flood and erosion hazards remain the same, or are even mitigated, and to plan and optimize the expected end situation. In the planning stage of the construction and during the construction itself, neither the analysis of the situation in the individual construction phases nor the impact of temporary facilities and measures (e.g. access roads, bridging structures) must not be neglected or deficient. It can be the case that compared to the completed structure, particularly in major and complex projects, intermediate construction phases can have significantly more adverse impacts on the runoff regime and therefore on flood and erosion hazards of the construction site and other users in space. A hydraulic analysis to determine the extent of flood, velocity or erosion forces flow distribution, and the changes in the entire runoff regime in the area in question is used to determine any potential hazards and adjust or optimise the planned construction phases of the individual structures and accompanying developments, so that risks and costs are reduced. The hydraulic analysis results of the individual phases allow us to assess the risks under transitional, changing spatial conditions compared to the condition prior to the construction and that after its completion. If excessive deterioration of the 1136