Barrage de Lavalette, Dam on the Lignon du Velay in Haute-Loire, France

Lavalette Dam is a concrete structure built across a valley in the Haute-Loire region between the villages of Lapte and Saint-Jeures. The construction holds back a large reservoir that supplies water to surrounding communities and contributes to local electricity production.

Lavalette Dam succeeded the Gouffre d'Enfer (1866) and Pas de Riot (1878) dams, each holding only 1 million m³. It was filled in the 1910s, and after the Second World War its wall was raised by 8 m, taking the reservoir from 5.5 to over 40 million m³. After the Lignon floods of 20–21 September 1980, a fourth and final gate was added.

The dam supplies drinking water to Saint-Étienne through the Chapelette dam and generates electricity at the Versilhac hydroelectric plant.

The dam lies between Lapte and Saint-Jeures, 15 km east of Yssingeaux and roughly equidistant from Le Puy-en-Velay and Saint-Étienne. A road runs along the 505 m crest, so the reservoir and the ski-jump spillway in the middle of the wall can be seen from above. The four sector gates control flood releases.

The dam's spillway is shaped as a ski jump in its middle section, so floodwater leaps clear of the downstream face. The crest carries a road, and the wall holds 180,000 m³ of masonry: rubble set in lime mortar for the older part, cement concrete for the postwar raising.