REPORT ON FLOODS OF 1865-1866. 229 



overflow its banks, its waters may cover the plains, destroy some crops, 

 and damage dwellings, but all of these damages are easily repaired, if they 

 repair not themselves when the waters recede within their banks. Rivers 

 like the Loire and the Allier, which come from granite mountains which 

 have been for a long time stripped of woods, do not act so. At every flood 

 they sweep away with themselves enormous masses of sand and of pebbles, 

 which they spread over the cultivated fields, thus rendering them for ever 

 unproductive. The bed of these rivers, constantly filling itself up with this 

 debris torn from the mountains which they traverse, is of no depth ; and 

 their thalweg, being without any fixity, is displaced at every flood, passing 

 into grounds which speedily disappear, carried away by the current. Now 

 there is no better preservative of rivers against the filling up with sand than 

 the fixation of the soil of the mountains by means of reboisement, or of 

 gazonnement, or of barrages, and works tending to moderate the flow at the 

 origin of the water-courses — that is to say, at the very source of the evil. 



" The experiment has been made, and now we can forsee from the present 

 that that day is coming when vegetation, drawn again over the slopes of 

 the mountain, shall have consolidated the surface, — when the torrential 

 water-courses shaU have been diverted from these, and shall no more carry 

 their dejections to the sea, — when all the old ravines shall have been stopped 

 up, and the valleys and cultivated plains shall have almost nothing to 

 dread from the violence of inundations." 



In a subsequent part, of the report, attention is called to the difference 

 between the expense and the extent of the work of reboisement and gazonne- 

 ment in different regions, which is pretty considerable ; and the Director- 

 General of the Forest Admistration goes on to say,—" These differences 

 result generally from the nature of the works executed. Where the rooks 

 which constitute the soil of the mountains present a sufficiently solid base, 

 and where the water-courses do not charge themselves with great masses of 

 disintegrated material, the operations ought to consist principally in the 

 creation of vast extents of woods, or of dense herbage, destined for the 

 retention of the vegetable earth, to fix it perinanently, and as a consequence 

 to control the regime of the waters. Then the artificial works are only 

 accessory, and it sufficed, for the greater part of the time, to bring back 

 again upon the slopes the vegetation which the abuse of pasturage had 

 caused to disappear. But on other ground, as in the Alps in particular — 

 where the grounds, devoid of consistency, are constantly being undermined 

 by the waters, and in consequence crumble down on all hands — sowings 

 and plantations would be insufficient to remedy the evil, if the consolidation 

 of the soil were not previously secured by preparatory works, such as 

 barrages, facinages, sustaining walls, and water-leadings from the torrents. 



" These works, the complete efficacy of which has been demonstrated by 

 six years' experience, occasion indeed a pretty considerable augmentation of 

 the expense in the reboisement and gazonnement of those p^rimtoes in which 

 they are executed ; but no outlay would appear to be more justifiable, if 

 we take into account the vast extent of lands which are thus protected 

 against the ravages of the waters, a good way beyond the boundary of the 

 pirimfetres themselves. 



" It would be superfluous work to go over the different proceedings 

 adopted in the construction qf barrages, and other artificial works, in regard 

 to which the necessary details have already been given. I confine myself 



