Janneh dam (Liban)

Verification and optimization of flows and energy dissipation at the foot of the dam spillway

Client: EBML - Echelle: 1:80


The development of a minimum 38 Mm3 reservoir in the Jannah Valley is part of the development of existing water resources in all regions of Lebanon. The construction of the Jannah dam, located in the Jannah valley in the Nahr Ibrahim River, will provide drinkable water, hydropower and irrigation water supply. The dam is a concrete arch dam about 157 m high above foundation and 350 m long.

The central part of the dam is dedicated to the free surface flood spillway. This spillway, defined at detailed design stage, needs to be validated before construction by physical modeling, which is the most appropriate tool, especially in regard to the converging spillway and the downstream scour risk.

Aims of the physical scale model

The aim of the study on the scale model is the validation, if necessary, the optimization of the flood spillway (weir, bridge piers, converging channel, flip bucket, plunge pool). In particular, the model brings high level technical assistance to :

  • Check the hydraulic behavior of the spillway crest, the converging channel and the flip bucket,
  • Determine with accuracy the rating curve of the spillway for the main flood discharges,
  • Evaluate the energy dissipation and the scour risk in the plunge pool at the downstream toe of the dam,
  • If necessary, propose and test modifications of the flip bucket or the rock protection in order to optimize the hydraulic design.