80 Transactions. — Miscellaneous. 



The Hurunni and Waiaii-ua are both, and especially the latter, very 

 large rivers, each draining an immense area of the steep mountain 

 masses which form the northern extension of the Southern Alps, and 

 each is subject to heavy floods, especially dming north-west summer rains. 

 The Pahau, though ordinarily an insignificant stream, is also liable to 

 heavy floods, not only because it drains a large mountain tract, but also 

 because in the area which it drains the mountains are exceptionally steep, 

 and the rainfall necessarily finds its way very rapidly into the minor water- 

 courses which supply it. The Weka Pass road debouches on to the 

 Hurunui Plain at a point where there is yet an undisturbed level portion of 

 the old lake bed, from the top of which it descends into the channel of the 

 Waikari, a small tributary of the Hurunui, which flows along the base of 

 the mountains on the south side of the oval. This tributary has also cut 

 its channel through the old lake bed, and has a small terrace on its 

 northern side, between which and the channel of the Hurunui the ground 

 rises gradually to the westward. On arrival near the latter channel we find 

 a terrace similar to that on the north side of the Waikari, below which Ues 

 the main bed of the Hurunui river. Crossing this bed, which is here 

 upwards of half a mile broad, we come to a high terrace, on ascending 

 which we reach the level ground which I have referred to as lying between 

 the two main rivers. The sm'face of that portion of the plain which lies 

 between the Waikari and Hurunui rivers is, as already stated, a good deal 

 lower than that of the original lake bed, as both rivers have been engaged, 

 ever since the lake basin was emptied, in removing the sands and gravels of 

 which it was composed, but this surface rises gradually towards the western 

 end of the oval, where it lies at the same level as the upper surface of the 

 plain between the two main rivers. 



On reaching the point at which the second gorge of the Waiau-ua opens 

 out to view, the road leads downwards over a succession of small terraces 

 to a main one bounding the high flood-channel of the river, the whole of 

 the gravels and sands below the original surface-level of the lake bed having 

 been removed from this part of the oval, besides which the river, in its 

 course through the gorge, has cut through the solid rock, underlying these 

 gravels, to a depth of from twenty to thirty feet. The gorge itself between 

 the Waiau-ua and Hanmer Plains is about eleven miles long, and rarely 

 more than a quarter of a mile in width, from the foot of the hills on the one 

 side to that of the hills on the other, the greater part of the river channel 

 being in solid rock overlaid by gravels disposed in terraces, corresponding 

 with those above described. The road through the gorge runs along the 

 surface of a main terrace on its western side, the gravels of which imme- 

 diately overlie the rocky walls between which the waters now flow. 



