[Pboc. Rot. Soc. Victoria, 35 (N.S.), Pt. II., 1923). 



Art. XIV. — The Increasing Run-off from the Avoca 

 River Basin (due apparently to Deforestation). 



• By E. T. QUAYLE, B.A. 



(With one Text fig.) 

 [Read 9th November, 1922] 



Some consideration has been given to this in a previous paper 

 dealing with the Control of Climate by Human Agency. This, how- 

 ever, was very casual and depended mainly upon the writer's impres- 

 sions, which are based upon recollections going as far back as 1870. 



The chief, points of interest are: — 



1. The flooding of the river, 



2. The duration of the flow each year, 



3. The minimum flow each month, 



4. The actual run-off. 



These are obviously influenced by the changes wrought through our 

 occupation of the drainage areas of the river, which dates back only 

 for about 60 years. Such pastoral use as had been made of it for a 

 few years previously was probably negligible in its effects. 



Physiographic Changes. 



The recent changes in the stream beds, which appear to have 

 begun about 1880, have been most striking. Up till about that time 

 large waterholes, many of which were 20 to 40 yards long, 10 to 

 15 yards wide, and 8 to 10 feet deep, were a feature of the streams, 

 and occurred at very short intervals, usually of only a chain or two. 

 The channels connecting these were almost always very shallow. One 

 old resident of Amphitheatre, a lady, testified that she was able, in 1861, 

 to step across the Avoca River, or Glenlogie Creek anywhere. For the 

 next 30 years, or until the early 'nineties, the changes in the channels 

 of the Avoca River, above the town of Avoca, and in. its tributaries 

 generally, were not particularly noticeable, but during the last decade 

 or two have become very marked. The destruction by stock of the 

 reeds and coarse grasses lining the channel, and the removal of logs 

 and growing trees, have permitted the beginning of erosion, and this 

 has lately become rapid. The effect is a double one. The aquatic 

 grasses which often covered the beds of the smaller streams, and the 

 coarse grasses and trees which lined the beds being destroyed, the cut- 

 ting of the channel began. This gradually lowered the level of the 

 water in the water holes, and now in most cases has almost com- 

 pletely drained them. When the flow is rapid, a fairly deep and. 



