IA\78 EfiaULATlNG RBBOlSBMBNt. 341 



The works by which it has been accomplished have been mainly those 

 recommended by Surell : — 



First, the formation of zones de defence, or zoTies de defends. Zones along 

 the main channel of a torrent, and ramifications of this in the basin drained 

 by it — the former enclosed, the latter simply protected by prohibition of 

 trespass by pasturing sheep or cattle thereon. 



Second, boisement — the planting of some of these zones more or less 

 extensively with trees and shrubs. 



Third, gazonnement — or the creation of what, in contradistinction to dead, 

 crumbling, denuded slopes, were called herges vives, by promoting the growth 

 of a dense covering of herbage. 



Fourth, the construction of barrages, or wears, generally of facines, &c., 

 but in some cases of stone, to arrest the current and so to prevent erosion, 

 and to arrest detritus in its progress towards the valley. 



At first, and for a time, it was intended that the zones should be 

 enclosed; but, with the modification of the law of 1860, introduced by that 

 of 1864, which substituted to a great extent gazonnement for boisement, it 

 was considered enough, except in some special cases, to prohibit the admit- 

 tance of flocks within the area of operation. And it was found, that the 

 zone left to itself, or sown broadcast with appropriate seeds, by degrees 

 became covered with a natural turf of herbage and bush. 



The berges vives generally take the form of rounded, elongated banks, 

 which become in like manner clothed with verdure. The object aimed at is 

 to give to a transverse section of the valley a stable waving outline, by the 

 bringing down of unstable elevations, and filling up with the debris inter- 

 vening depressions, converting the acute, projecting, and retiring angles 

 which they generally form into connected curves. This operation was 

 sometimes effected on an extensive scale by blasting, but in general the 

 pickaxe could do all that was required. 



Simultaneously with this operation has been carried on the erection of 

 barrages where necessary. 



The barrages, or barriers or wears, were designed to arrest and retain gravel 

 which might fall or be washed dowii slopes, and so to prevent its reaching 

 the cone de dejection to add to accumulations there. The structure of them 

 varied with the material at command, and the requirements of the situa- 

 tion. There are barrages of large blocks of stone in solid masonry, held 

 together by iron clamps ; there are dry stone dykes ; there are some 

 barrages formed of stakes, and of wickerwork or hurdles ; and in acute 

 angled beds of currents, there are laid in the bottom beds of fagots and 

 stone, over which are spread the debris of demolished surmounting hills ; 

 and sometimes a simple gabion is placed in the thalweg, with its mouth 

 directed up stream, and left like a bow-net in that position to be filled 

 with earth by the flood occasioned by the first storm of rain which may 

 come ; and sometimes for this there is substituted a tree or a bush half 

 buried, with its branches and roots in the bed of a stream. All that is 

 sought to be done is, with the readiest materials to adapt the barrier to 

 the requirements of the locality, giving it strength proportionate to the 

 strain ; and in some cases a turf or tuft of grass may suffice. 



The importance of giving fixity to the hills, in combination with the 

 arrest of debris by barriers adapted to the locality, can, perhaps, only be 

 realised fully in view of the landslips, of a greater or less extent, constantly 

 occurring. In view of these, the arrest of the debris by the barrage was 



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