Harpefoss is a rapid in the Gudbrandsdalslågen river, near the municipality of Sør-Fron, Norway. The water is very calm here, but Norwegian rivers 'crest' in the spring when the snow melts. The Gudbrandsdalslågen, which drains higher elevations and is fed mainly by glaciers, usually has this high-water moment later than the Glomma River, which drains the water from eastern valleys. In the rare year when both crest at the same time, their confluence at Nes is the site of major flooding. The most famous simultaneous crest of both rivers resulted in a flood on 20/23 July 1789, with peaks of more than 50 feet above average level and a lot of damage in the vicinity of Nes, with 68 casualties.