80 Transactions.—Miscellaneous. 
The Hurunui and Waiau-ua are both, and especially the latter, very 
large rivers, each draining an immense area of the steep monntain 
masses which form the northern extension of the Southern Alps, and 
each is subject to heavy floods, especially during 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 les 
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 surface 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 immé- 
diately overlie the rocky walls between which the waters now flow. 
