The Gudbrandsdalslågen (or simply Lågen) is a river which flows through the Gudbrandsdal valley in Innlandet county, Norway. The long river runs through a large valley in Eastern Norway before emptying into Mjøsa, the largest lake in Norway. The river flows through the municipalities of Lesja, Dovre, Sel, Nord-Fron, Sør-Fron, Ringebu, Øyer, and Lillehammer. Watercourse The Gudbrandsdalslågen begins in the lake Lesjaskogsvatnet (or Lesjavatn), which lies in Lesja municipality in the far northern part of the county. Lesjavatn is the only lake in Norway which has two outlets, and they both flow into two of Norway’s more famous rivers. In the southeast at the village of Lesjaverk, the lake serves as the headwaters for the Gudbrandsdalslågen, while in the northwest at Lesjaskog village, Lesjavatn is the headwaters for the Rauma river which heads to the west. The Gudbrandsdalslågen river flows through the Gudbrandsdal valley. Western tributaries of the Gudbrandsdalslågen include the Gausa River flowing through the Gausdal valley, the Otta River flowing through the Ottadalen valley, the Vinstra River flowing through Vinstradalen, and the Sjoa River, flowing through the Heidal valley. The eastern rivers, Jora, Ula, Frya, Tromsa, and Mesna are shorter and drop precipitously from the heights of the Rondane mountains. Although relatively placid for extended stretches of its path, the Gudbrandsdalslågen drops rapidly through the Rosten Gorge in Sel Municipality. Between the municipalities of Ringebu and Øyer the river widens out and creates the large so-called "riverlake" Losna). The Gudbrandsdalslågen terminates in the lake of Mjøsa at the town of Lillehammer. It is the largest river flowing into this lake. The lake which discharges into the short Vorma River which in turn flows into the Glomma River at Nes. Flooding Norwegian rivers crest in the spring as the snow melts. The Gudbrandsdalslågen, draining higher elevations and being primarily glacier fed, typically crests later than the Glomma river, which drains the east valleys. In the rare year when both crest at the same time, their confluence at Nes is the site of great floods. The most famous simultaneous crest of the Gudbrandsdalslågen and Glomma rivers resulted in the flood that took place on 20–23 July 1789, with crests over above the average level of the water. At the lake Øyeren which is beyond Nes there was extensive damage, including 68 casualties. Bridge Collapses In 2016 Perkolo Bridge over the Gudbrandsdalslågen at Soja collapsed.The bridge was made of glued laminated