424 APPENDIX 



The forestation of the two slopes and part of the cone have very much improved matters, 

 but, with such a topography, it is certain that it will always produce dangerous and 

 sudden floods. The Daret, commune of St. JuUen, flows from north to south to a point 

 southwest of the Rieu-Sec. On the left it is joined by three ravines which originate 

 in the Croix des Tetes. Its basin is formed by gypsums, limestone, and schists. As 

 in the case of the Rieu-Sec, the dams have been constructed of blocks of stone each 

 about 1 cubic yard in volume. Several drainage canals and forestation of spruce, larch, 

 and mountain pine complete the control work started by the dams. The St. JuUen 

 torrent (see page 156), commvmes of St. Julien and Mont Denis, is a vast and complex 

 torrent. Its basin comprises some 4,940 acres and is cut by ravines eroded in the schists, 

 glacial muds, and marls. AU this kind of soil is easily eroded. The floods and lava 

 flows of St. Julien have been very numerous and have caused tremendous damage. The 

 diversion canal, cut in the rock, has stopped a vast landshde which threatened the 

 viUage of Mont Denis. Dams below and above the source of the damage have fixed 

 the bed of the torrent and its waters are now conducted to the Arc by a drainage canal. 

 Forestation of Scotch pine, oak, and ash has been completed in the sUde area and plan- 

 tations of poplar, willow, and alder have been made in the gorge. It appears that 

 considerable damage has been reduced to the minimum. The torrent of Rieu-Bel, 

 communes of Albiez-le-Jeune and Villergondran, rises in the commune of Albiez-le- 

 Jeune at an altitude of 5,085 feet. It runs north for a length of more than 2 miles. 

 Its circular upper basin is cut by little ravines which reunite in one big torrent below 

 3,600 feet altitude. The soil comes from the disintegration of schists, usually saturated 

 with water and shows a tendency to slide. By its floods and rockfall the torrent of 

 Rieu-Bel menaces the village of Villergondran. Rough dams have been constructed 

 to fix the bed of the torrent and drainage canals have been established with a view to 

 draining the soil. Plantations of spruce and larch, not yet thrifty, completed the work, 

 which, however, must be continued. 



The torrent of Roches Noires, communes of Villergondran and St. Jean de Maurienne, 

 is cut in the black schists and in the glacial drifts. The steep slopes and the sterility 

 of the soil have rendered the forestation difficult and uncertain. Everywhere the bed 

 had to be fixed with wattle work but even then vegetation could not be introduced. 

 Forestation is more important in this perimeter than in those which have already been 

 described. The area forested includes some 1,599 acres. The corrective work, which 

 remains to be finished as soon as possible, is Umited to the construction of dams at the 

 base, and the estabhshment of Uttle accessory dams. 



Forestation Area of la Blanche. — The torrent of the Blanche is a tributary of the 

 left branch of the Durance which rises in the southeast of Sejnae at the summit of Roche 

 Close. It runs from the east to the west to the hamlet of Chardavox, when it turns to 

 the northwest and follows into the Durance after a course of 19 miles. From the 

 hamlet of Vi^rard (commune of Saint-Martin-les-Sejme), or until it joins the Durance, 

 this stream follows through narrow rocky gorges and b called the torrent of Rabious. 

 Its drainage area belongs to the sub- Alpine region; it is bounded on the east by a very 

 high chain of mountains, called la Blanche, whose altitude varies from 7,220 to 8,860 

 feet. . . . Taking the basin as a whole, the Blanche has no important tributaries, 

 but several of them, because of the tremendous slopes, are dangerous torrents. The 

 greatest altitude is that of the Pic de la Blanche (9,075 feet) and the lowest is at the 

 confluence with the Durance and Rabious (2,149 feet). 



Geological Conditions. — The bottom of the Blanche basin is occupied by glacial 

 deposits from which emerge black marls. ... At the extreme southeast of the 

 valley there is a great deal of limestone soil. ... On account of the predominance 

 of the glacial deposits under the black marls which form soil very susceptible to erosion, 

 this basin is, on all sides, composed of deep ravines and sharp hills. . . . 



