112 Transactions. 



great a cost as to exclude the probability of their being carried out either by 

 the residents on the flooded area or the Government ; while there is one 

 which has been mooted upon several occasions, but dismissed almost as soon 

 as mentioned, which appears to me worthy of more consideration. Having 

 had for some time the feeling, scarcely raised to the position of an opinion, 

 that the proposal to form a store reservoir at the Taieri Lake had not 

 received sufficient attention, I took the opportunity, while in that neighbour- 

 hood last December, of spending some hours in making a careful examination 

 of the physical features at the outfall, and J now propose to investigate how 

 far the damming back of the waters of that part would tend towards the 

 prevention of those disastrous floods to which the Taieri plain has been 

 subjected in late years. Unfortunately, I have not at command sufficient 

 information either as to the rainfall or the configuration of the ground, to give 

 exact quantities in dealing with the whole of this subject ; but for purposes of 

 preliminary enquiry we may find enough either from direct observation or 

 from general laws which may bear upon the subject. In the following 

 calculations I have been much indebted to the elaborate survey executed in 

 connection with Mr. J. T. Thomson's report upon the subject in 1870, which 

 has been kindly placed at my disposal. Other parts are filled in from the 

 general map of the Province, and by personal observation. 



Before considering the case I shall glance briefly at the nature and propor- 

 tions of the evil, for without a knowledge of these we cannot judge of the 

 feasibility of any proposed remedy. 



Referring then to the map of Otago, we find that the lower Taieri plain 

 lies at the mouths of the Taieri and Waipori rivers and the Silverstream, all 

 discharging large quantities of water during floods, especially the former river, 

 which has an outpour per minute through the gorge at Outram, even at its 

 lowest, nearly equal to that of the Clyde in Scotland between Glasgow and 

 Port Glasgow ; but having a fall very much greater, the cross section is 

 correspondingly less. By computing the drainage areas of these local rivers, 

 we find that into the basin occupied by the Waipori and Waihola lakes, and 

 the Taieri plain, there is discharged that portion of the rainfall over 2065 

 square miles of country, which has escaped evaporation or absorption by plants 

 or porous strata, the relative areas being — 



Square Miles. 

 Taieri river ... ... ... ... ... 1,730 



Waipori ... ... ... ... ... 265 



Silverstream ... ... ... ... .... .70 



2,065 

 The Silverstream being comparatively small, and the waters of the Waipori 

 being discharged into the lake of that name, with an effect upon the floods 



