﻿DoBSON. — On Destruction of Land hy Shingle-hearing Rivers. 155 



the case is very different in open country, wliere there is nothing but grass to 

 check the flow of water on the surface. After saturating the soil the water 

 rushes without hindrance into the nearest hollow, and, rapidly accumulating 

 volume and velocity, soon forms a dangerous and foaming torrent, which, 

 cutting into the surface of the ground, carries down large quantities of gravel 

 and detritus into the nearest river. 



Whenever a river, for the greater part of its cotirse, -runs through a wooded 

 country, the changes are effected so slowly in the river bed that the vegetation 

 has ample time to take possession of any ground the river may abandon and 

 convert it into forest land ; the scriib and undergrowth also retain the silt 

 borne amongst them by the floods, so that the banks and lowlands are raised 

 and fertilised by every inundation. All this, however, is totally changed as 

 soon as settlement commences and man begins to clear the timber and cultivate 

 the soil. The timber is frequently taken from the river banks first, from the 

 facility of transport by water — cafctle feed on and destroy the scrub which clothes 

 the banks, which, dentided of the natural covering, become an easy prey to the 

 action of floods — every ditch that is dug increases the rapidity with which the 

 rainfall is carried into the river, and the floods necessarily rise higher than 

 before from having to carry off a greater body of water in the same time ; as 

 the clearing is carried further inland and the hill sides are bared, the water, 

 during rains, can collect rapidly in all the small gullies, which will be con- 

 verted into foaming torrents, and, no longer prevented by roots and moss from 

 abrading the surface, they carve deep gullies in the mountain sides, bearing 

 down enormous quantities of broken stone and gravel into the main stream 

 below, which, in its turn, will carry on the detritus as far as the strength of 

 the current permits, and then throw it down to fill up the river bed, and add 

 to the destruction already in progress by the ciitting away of the river banks. 

 The enormous devastation occasioned by the indiscriminate destruction of 

 forests in the Old World is so clearly shown by Mr. Gr. P. Marsh, in " Man 

 and Nature," that I must refer to his work, as it gives a far better idea of the 

 evUs to be apprehended from the destruction of forests than any description of 

 the devastations at present in progress iii this province. 



His descriptions show that most disastrous results may be expected from 

 the felling of timber in the valleys and on the mountain sides in this province, 

 unless steps are taken to prevent the evils thus occasioned by renewed planting, 

 and the conservation of the forests in the upper course of the streams. 



The town of Nelson, standing as it does on the banks of a mountain 

 torrent, is particularly liable to damage from inundations. Floods which have 

 already occurred show the amount of damage even a small stream can do 

 in a few hours, when flooded and heavily charged with detritus. Owing to the 

 inaccessibility of the valleys of the Maitai and the Bi-ook, but little clearing 



