Barr. — On the Taieri Floods. 113 



only in connection with the Taieri, I shall simply refer to them at that stage 

 when we come to view the storage room on the lower parts of the j)lain, and 

 shall devote this portion principally to the nature of the larger river and its 

 floods. 



A comparison of the Taieri with the chief rivers of Europe or Noi"th 

 America will show that in proportion to the country drained it is much in 

 excess of the most of these as a flood producer. Thus, while it pours down its 

 water at the rate of 1-666 cubic yards in the second for each square mile 

 drained above Outram, the Mississippi in flood flows only at the rate of 0"044 ; 

 the Ohio, at its mouth, 0-122 ; and the Yazoo 0-372 cubic yards per square 

 mile drained. In Great Britain, the Tyne is the only one which approximates 

 to the Taieri in this respect, its rate of flood discharge being 1*12 ; but small 

 streams which have been gauged in meadow land have yielded as much as 1 -2. 

 The Yellow River, in Ireland, is as high as 4-12. On the continent of Europe 

 the Loire appears to be pre-eminent for its floods — yielding at Pont de Fleurs 

 as much as 4*18 cubic yards j)er second for each mile drained. Many of the 

 Indian rivers far exceed any of the above — the Irvitz, especially, deKvering at 

 the rate of 16-5 cubic yards per second for each square mile of its gathering 

 ground. 



Now these figures of course represent very rough comparisons between the 

 several streams named, no two of which are alike in physical conditions, 

 either as to amount of rainfall or configuration of drainage area ; but in 

 a general way they enable a classification to be made which may yet be 

 further improved as information is gathered. Apart from the relative 

 quantities of rainfall, there are many other circumstances which tend either to 

 aid or impede floods. Thus a stream draining a large tract of country is much 

 less liable to heavy floods than one draining a small one ; and also the general 

 nature of the country as to inclination has a most noticeable effect upon the 

 rate at which the water finds its way to the river, and consequently a like 

 effect upon the amount of its volume. Another most important consideration 

 is the nature of the strata, or the amount of vegetation in the district drained ; 

 for when the rocks are of a close compact nature, with comparatively few 

 joints or crevices, and the ground bears but little vegetation, the water will 

 run quickly oflf ; but where the ground is porous, and the vegetation rank, a 

 much longer time will elapse before the underground basins are filled, and the 

 ground so saturated as to shed the water off" as the rain falls. Surface lakes 

 have a comparatively greater effect in raoderatirjg floods than either of the 

 above causes, by receiving the water as it comes from the creeks, and allowing 

 it to spread in thin films instead of rushing down a river channel in deep 

 volumes. 



Having got these general results, we may now endeavour to examine 



p 



