The diagnosis of the Tamesna Dam, shows that the surrounding land of the dam is particularly affected by natural hazards:

Landslides affecting the sedimentary sequence quartzite/schists (trends of the rocks and the slopes clearly control their occurrence),

Landslides of the road section,

Shallow landslides developed in the slope covered by residual soil,

Rock falling freely from steep and vertical slopes.

Due to the important role of geology and rock weathering in the instabilities, an attempt has been made to understand the relationship between these phenomena. The frequent instabilities in the area of the Tamesna Dam are controlled by the trends of the rocks and slopes, the structural features, the rock lithologies, weathering and exceptional rainfall (percolation of rain water through highly jointed rocks and slope equilibrium disturbances).

The rock formation in the area of the dam consists essentially of quartzitic bars alternating with decompressed schists attributed to the Carboniferous. The 33direction of the stratification planes varies substantially between N85° and N100° and the dip is 30° to 40° downstream. Three fracture families affect the quartzitic rock: N20/vertical, N55/58° S and N15/71° SW.

The bedrock is covered by residual soil and/or colluviums.

Several solutions have been proposed to assess the landslide hazards. The solutions chosen after a comparative study were the following:

Removing instable material (debris and rocks),

Mechanical or explosive bleeding of large, unstable blocks,

Re-profiling the slope,

Shotcrete and welded mesh,

Applying grid and installing anchors,

Installing drains,

Rockfall protection barriers,