The storage level of the retention is raised to the level of the panel discharge crest. When the reservoir is full, the flood flows over the crest of the folding fusegate, which acts as a free threshold (Fig. 1).
When, during major floods, the upstream water level reaches the crest of the supply well (in an annex structure), the negative pressure chamber is supplied (Fig. 2).
The negative pressure force generated in this chamber actuates the tilting mechanism of the folding fusegate. The panel folds in order to discharge the flood (Fig. 3).
The tilting rate of each panel is precisely adjusted by the admission well height setting. After a major flood has passed, the panel set back into its original configuration.