478 



Canadian Forestry Journal, April, ipid. 



brought down by the water, prevents 

 the carriage of gravel and rock to the 

 stream below, and prevents erosion. 



Bracing Up a Stream Bed. 



At other times when branches are 

 not available barriers of faggots, sods 

 and stone are constructed at frequent 

 intervals across the bed of the stream, 

 the purpose of which is to hold up the 

 water, catch sediment and prevent the 

 cutting of the stream bed or banks. 

 The barriers are rendered permanent 

 by planting with shrubs or with cut- 

 tings of such species as willow and 

 alder, which strengthen the banks, 

 protect the bed of the stream, and 

 form a living network of branches and 

 roots to hold back flood waters and 

 their burden of earth and rock. 



Those portions of streams in which 

 a large volume of water is tlowing, 

 wdiere the bed and banks are rapidly 

 cutting, and where torrential charac- 

 teristics have already developed, re- 

 quire more serious treatment. In such 

 cases masonry walls are built with the 

 object of impounding the products of 

 erosion, checking the headlong flow of 

 water, preventing the cutting down of 

 the bed of the stream, supporting un- 

 stable banks. The bed banks and 

 flow of the stream are carefully stu- 

 died before work is begun, 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 fur- 

 ther that the detritus accumulated 

 by the masonry will prove an indirect 

 support to shifting banks and a valu- 

 able means of decreasing the grade 

 and checking the speed of the stream. 

 According to the gravity of condi- 

 tions, the barrages vary from simple 

 dry stone sills set across the bed of the 

 stream a few feet apart to mortar-set 

 stone walls three feet or more thick, 

 fifteen feet high, crossing the stream 

 from bank to bank set so close togeth- 

 er 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 wa- 

 terflow, or create new stream beds 

 than to correct the torrent by barrages ; 

 where necessary this is done. Occa- 

 sionally also the constant sliding in of 

 stream banks crushes the strongest 

 barrages. Draining is then resorted 

 to on a large scale in order that the 

 banks may be fixed. 



Preventing Snozcslides. 



The prevention of avalanches and 

 snowslides is also undertaken. Snow- 

 slides usually follow definite courses. 

 Stone walls five to six feet high, two 

 and a half feet thick, are built across 

 the upper courses of dangerous snow- 

 slides beginning at the point whe're 

 the avalanche usually takes its start 

 anfl continuing down the slope in 

 ranks to the point below which snow- 

 slides are unlikely to start. \\'hen 

 stone walls are impracticable, the de- 

 sired results are secured by low banks 

 of loose rock or earth disposed in the 

 same manner. When conditions per- 

 mit 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 correc- 

 tive works constructed up to 1909 ex- 

 ceeded the cost of reforestation on 

 the same streams, being over $6,560,- 

 000. including maintenance to the 

 same date. The question of mainte- 

 nance 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 wavs, by employing them on the 

 works by mone_y grants for pasture 

 improvement, and by subvention to 

 creameries and co-operative dairy 

 associations. The total amount of 

 such expenditure is about $35,000 

 chargeable 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 



