| Sarp Falls | |
|---|---|
.JPG) Sarpefossen in May 2014 | |
  Location within Norway South | |
| Location | Østfold county in southeastern Norway |
| Coordinates | 59°16′34.0″N 11°7′51.22″E / 59.276111°N 11.1308944°E |
| Total height | 20.5 m |
Average flow rate | 577 m³/s |
Sarp Falls (Norwegian: Sarpefossen or Sarpsfossen) is a waterfall at Sarpsborg in Østfold, Norway. It is the second largest waterfall in Europe by discharge, after the Rhine Falls.
This is the last waterfall on the Glomma River, which is the longest river in Norway. The waterfall has a total vertical drop of approximately 20.5 m (67 ft). Its large discharge is a consequence of the extensive drainage basin of the Glomma above Sarpsborg, which covers approximately 41,182 km2 (15,900 sq mi). During major floods, the waterfall and its associated river channels can carry several thousand cubic metres of water per second.
The falls have played an important role in the history and development of Sarpsborg. The location was associated with the foundation of the medieval town of Borg by Olav Haraldsson in 1016, and the waterfall later became an important source of mechanical power for mills and sawmills. From the late 19th century onward, the waterfall became a major source of hydroelectricity and helped attract large-scale industry to the area.
Sarp Falls is situated where the Glomma passes through the Østfoldraet, a major moraine ridge formed during the Last Glacial Period. The moraine obstructs the river's natural route and forces the Glomma toward the east, where it passes over a bedrock threshold and forms the waterfall.
According to Sarpsborg municipality, the present waterfall developed when the Glomma broke through the moraine ridge approximately 4,000 years ago. The formation of the falls created a distinctive geographical boundary between areas to the north and south and contributed to the importance of the site as a settlement and transportation location.
The Glomma is Norway's longest river. Immediately north of Sarp Falls, the river system divides into several branches. The principal eastern branch passes through Sarpsborg and over Sarp Falls, while another branch passes through Mingevatnet, Vestvannet and Visterflo before rejoining the main river system farther south.
The drainage basin of the Glomma above the waterfall covers approximately 41,182 km2 (15,900 sq mi). The large catchment contributes to the exceptionally high discharge of the falls compared with many other European waterfalls. The average flow at Sarp Falls is approximately 577 m3/s (20,400 cu ft/s), although the discharge varies considerably with season and precipitation.
The flood-discharge capacity associated with the falls is approximately 3,400 m3/s (120,000 cu ft/s).
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