Dam rehabilitation study with process oriented numerical flow models

In the global framework of climate change, hydraulic structures rehabilitation is an up-to-date subject requiring appropriate design and impact studies. In this scope, upgrading the release facilities of dams is an important point when both up and downstream consequences, often irreversible, of badly controlled rising of water in the reservoir, become awarded. Suitable numerical models, coupled with contemporary computational possibilities, allow engineers to forecast the complex situations induced on real structures by extreme events with increasing representativeness and accuracy. In this field, WOLF software, a process oriented free surface flows computation package completely set up by the HACH, has proved its efficiency and reliability for years by numerous theoretical, experimental as well as on real structures applications. In this paper, the rehabilitation study of the Nisramont dam (Belgium) is presented. Due to its temporary primary tasks, the stilling basin downstream of the crest spillway has been designed for a short time use. It’s the same with the 3 bottom outlets, which were never equipped with valves and are thus unusable for the reservoir management. In order to secure the structure and to make it comply with its definitive working objectives, while taking into account climate change observations, the HACH has been entrusted with evaluating up to date critical flood discharges and with designing a system in accord with these new values for the rehabilitation of the bottom outlets and the evacuation of the floods. Several construction options have been compared and optimized by means of the hydrodynamic software WOLF.