Torrent du Manival is a shallow mountain stream down from the Chartreuse range that can be misleadingly dangerous when dry. During a thunderstorm the water level rises quickly and the stream tears and brings down everything on its way. Major protection works  started in the end of 19th century, not only to control the flow of water but solids as well, in particular fine clay material that forms torrents of mud — like lava flows — which could be disastrous  to buildings and roads downstream, since they can move very large blocks of rocks. Today, starting at the altitude of 1250 meters,  the torrent is equipped with huge stair-like structures that prevent the erosion of the banks, slow down the mud flow, and help sort the material coming down, so that the water brings the finest pebbles further down.

Today’s hike, which literally started from our doorsteps, took as to the stream of Manival.  There are hiking trails, with information boards, running on both sides of it. We climbed up the right bank on a trail that balanced on a steep slope above the stream, and came down the left bank on a wide forest road (12.3K in 4h, D+/D- 666m). The landscape at the beginning of the climb resembled that of a Western movie set.