Barr. — On the Taieri Floods. 115 



followed some months of comparatively dry weather, though it commenced one 

 showinsj a total of 7*399 in. 



Floods may also suddenly arise after a drought, from the fact of some kinds 

 of soil being so thoroughly baked as to have a surface almost as impervious 

 to rain as rock itself, and thus it delivers the water almost as it falls ; but 

 such floods will be of short duration, and only until the surface has had time 

 to soften a little and allow the usual amount of soakage. 



I have referred to the raiufall at Dunedin, because unfortunately we have 

 no records of its amount for the Taieri basin, and if we were wanting to go 

 minutely into the matter, as we shall see immediately, the rain gauge in this 

 city would be apt to mislead rather than enable us to arrive at correct results. 

 Those who have paid any attention to meteorology must be aware of the great 

 diversity of rainfall in different districts, even within a few miles of each 

 other, and consequently of the necessity for separate observations in various 

 localities, if any practical result of value is to be evolved. We are safe 

 enough, however, in taking the evidence of the Dunedin observations to prove 

 generally a season of unexampled moisture within the Taieri basin ; but it will 

 be seen by a study of the figures representing the flow of the Taieri during the 

 flood of 1868, that for particular occasions they are of little value. Thus, for 

 the flood of January 28th, a fall of 1-648 in. was shewn, yet that did not raise 

 the Taieri river so much as a fall registered as 1 '37 in. did a few days after- 

 wards. This, however, does not completely prove the position that the 

 Dunedin register is different from what the Taieri one would be, for it is still 

 possible that the whole area of the gathering ground was not saturated to its 

 fullest extent on the 28th January, so that a greater degree of saturation, as 

 on 4th February, would greatly aid the rain of the latter date in producing a 

 flood greater than the one a few days previous. Better proof, however, is 

 found in referring to the delivery by the river at Outram, which, as recorded 

 by Mr. Thomson, was at the rate of 4,653,068 cubic feet per minute ; which 

 would show a fall at the rate of 1'67 in., instead of 1*37, even with the whole 

 water run off to the river just as it fell. Even this, however, is not quite 

 satisfactory, for it is quite possible, and indeed likely, that in both localities 

 there was a space of time — perhaps extending to hours — in which the rainfall 

 was of greater intensity than even the higher of these sums represents. As it 

 is impossible, however, to have the records for each few hours, we must 

 generalize from the most frequent, viz., those for each twenty-four hours. 



I shall now endeavour to ascertain the length of time which may be 

 considered as the duration of the flood, or how many hours elapsed between 

 the moment when the banks overflowed, and the outlet to the sea was too 

 small to allow the whole waters which were issuing upon the plain, and the 

 Waipori and Waihola lakes, to pass off. 



