Image Number 8 for United States Patent #5195846.
For the purpose of providing a more economical alternative to conventional control gates for the quasi-permanent closure of all or part of the length of the overflow spillway of a dam except when discharging extraordinary floods, the invention consists of installing on the sill of the spillway a water level raising means comprising at least one heavy element, held by gravity on the sill, the water level raising means or its element being designed to overturn at a predetermined head corresponding to a headwater level not higher than the predetermined maximum water level in order to discharge extraordinary floods, smaller floods being discharged by a separate flood discharge structure.
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