Canadian Forestry Journal, March, ig20 



banks. The barriers are rendered per- 

 manent by planting with shrubs or 

 with cuttings of such species as wil- 

 low and alder, which strengthen the 

 banks, protect the bed of the stream, 

 and form a living network of 

 branches and roots to hold back flo(jd 

 waters and their burden of carlli and 

 rock. 



Those portions of streams in which 

 a large volume of water is flowing, 

 where the bed and banks are rapidly 

 cutting, ;in(l where torrential charac- 

 teristics lia\c already developed, re- 

 (juire more serious treatment. In suc''i 

 cases masonry walls are built with 

 the object of impounding the pro- 

 ducts iif erosion, checking the head- 

 long flow of water, preventing th^' 

 cutting down of the bed of .the 

 stream, su]j])orting unstable banks. 

 The bed. banks and flow of the stream 

 arc carefully studied before work is 

 l)egun, and walls and barrages, as 

 they are called, are designed to meet 

 the requirements of each particular 

 case, both so that the masonry itself 

 may meet the stresses to which it will 

 be subject, and further that the detri- 

 tus accumulated l)y the masonry will 

 ])rove an indirect support to shifting 

 l)anks and a valuable means of de- 

 creasing the grade and checking the 

 speed of the stream. According to 

 the gravity of conditions the barrages 

 vary from simple dry stone sills set 

 across the bed of the stream a few 

 feet apart, to mortar-set stone w'alls 

 three feet or more thick, fifteen feet 

 high, crossing the stream from bank 

 to bank, set so close together that the 

 top of one wall is level with the base 

 of the next barrage above it. 



Sometimes it has proven easier to 

 pave stream bottoms, canalize the 

 waterflow, or create new' stream beds 

 than to correct the torrent by bar- 

 rages ; where necessary this is done. 

 Occasionally also the constant sliding 

 in of stream banks crushes the strong- 

 est barrages. Draining is then re- 

 sorted to on a large scale in order 

 that the banks may be fixed. 



Preventing Snowslides. 



The ])revention of avalanches and 

 snowslides is also undertaken. Snow- 

 slifles usually follow definite courses. 

 Stone walls five to six feet high, two 

 and a half feet thick, are built across 

 the up])er courses of dangerous sn nv" 

 slides beginning at the point where 

 the avalanche usually takes its start 

 and continuing down the slope in 

 ranks to the point below wiiich snow- 

 slides are unlikely to start. When 

 stone walls are impracticable, the de- 

 sired results are secured by low 

 banks of loose rock or earth disposed 

 in the same manner. When condi- 

 tions permit of it, plantations of trees 

 or shrubs are made under shelter of 

 the walls or banks. 



There have been very few torrents 

 upon which work has been done by 

 the French National Government 

 upon which some or all of the above 

 corrective works constructed up to 

 TQ09 exceeded the cost of reforesta- 

 tion on the same streams, being over 

 $6,560,000, including maintenance to 

 the same date. The question of main- 

 tenance is a serious one. All the 

 works require constant upkeep, and 

 some have had to be rebuilt several 

 times. 



The opposition of the mountain 

 population has been overcome in vari- 

 ous ways, by employing them on the 

 works, by money grants for pasture 

 improvement, and by subvention to 

 creameries and co-operative dairy 

 associations. The total amount of 

 such expenditure is about $3^,000 

 clrargeable to the fund for the correc- 

 tion of torrents. 



The work which the French have 

 undertaken, re-clothing the drainage 

 basins and remodelling the beds of 

 thousands of mountain streams, 

 should, when finished, rank with the 

 great constructive public works of the 

 world. The task is now^ half com- 

 pleted. The cost up to 1909 was 

 $20,650,000. The estimated cost for 

 the remainder of the w^ork in sight 

 was then $12,000,000, exclusive of 

 upkeep and exclusive of the expendi- 

 ture necessary by departments, com- 



