Risk assessment for the critical regimes of Chaira dam stilling basin

The estimation of potential hazardous operations of the stilling basin can be obtained after determining their critical regimes. The processes definition can be understood from the power point of view with a relative ease. At times, however, there is the possibility to observe several critical regimes for varying discharges. These regimes govern the design defining the dimensions of the stilling basin. The stilling basin of Chaira Dam Bulgaria is a good example demonstrating these different governing regimes. Several unfavourable effects are observed at different working regimes. This authors' work shows that predictions of the negative effects at the stilling basins is possible and necessary. This paper describes how the current Chaira Dam construction allows a unique possibility to observe and document extreme regimes for discharges less than the maximum level possible. These regimes, obtained for both small and large openings of the gate, are explored and explained in detail.