Gryonne
| Gryonne | ||
 Gryonne about 1 km before the confluence with the Rhône |
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| Data | ||
| Water code | CH : 3929 | |
| location | Canton of Vaud , Switzerland | |
| River system | Rhone | |
| Drain over | Rhone → Mediterranean | |
| source | west of the Culan 46 ° 18 ′ 27 ″ N , 7 ° 8 ′ 16 ″ E |
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| Source height | approx. 1700 m above sea level M. | |
| muzzle | near Monthey in the Rhône coordinates: 46 ° 15 '43 " N , 6 ° 58' 24" E ; CH1903: 564117 / 123494 46 ° 15 '43 " N , 6 ° 58' 24" O |
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| Mouth height | 395 m above sea level M. | |
| Height difference | approx. 1305 m | |
| Bottom slope | approx. 87 ‰ | |
| length | approx. 15 km | |
| Catchment area | approx. 37 km² | |
| Left tributaries | Ruisseau de l'Abbaye, Petit Gryonne | |
The Gryonne is a 15 km long right tributary of the Rhone in the Swiss canton of Vaud . It drains a section of the Vaudois Alps . The catchment area of the Gryonne has an area of about 37 km².
The source of the Gryonne is located at around 1700 m above sea level. M. below a rock face on the western slope of the 2789 m high Culan , which belongs to the massif of Les Diablerets . It lies exactly on the border of the municipalities of Ollon and Gryon, southeast of the Col de la Croix pass . The Gryonne flows west through the pastures of Alp Coufin and then deepens into a densely wooded, difficult to access valley that separates the terrace of Villars-sur-Ollon in the north from the heights of Gryon in the south.
In the middle reaches the Gryonne overcomes a height difference of almost 700 m over a distance of 5 km, which corresponds to a mean gradient of 14%. The torrent between Ollon and Bex reaches the Rhone Valley, on the eastern edge of which it has created a large alluvial cone over time . At the height of Monthey the Gryonne empties at 395 m above sea level. M. in the Rhône.
The Gryonne is characterized by a nival runoff regime . Several short side streams flow to the Gryonne from the surrounding slopes. The largest of these is the Petite Gryonne , which rises in the arena above Villars-sur-Ollon. The upper reaches of the Gryonne are largely preserved in their natural state. Along the middle course, torrent barriers were built at the steep points to fix the valley floor and to contain the deep erosion and the scree. The Gryonne was channeled, straightened and provided with thresholds in the lower reaches from the entry into the Rhone Valley. Dams were built as a measure to protect residential areas from floods.