Floods on the River Barwon. 113 



actually was. An inspection of the water as it flowed over 

 the model threw important light on some points of difficulty. 

 For example, the comparatively high water level at 

 Haworth's Tannery, which is on the downstream side of the 

 bridge, had been a source of a little perplexity, but on the 

 model the true constriction and most rapid fall of the water 

 was seen to be not under the bridge itself, but on a line 

 dravm from the south end of the bridge to the south-ivest 

 angle of the tannery. The width of the stream at this 

 point is less than half the length of the bridge. Another 

 point of interest that presented itself was the marked 

 effect of the piles of the bridge in breaking up the stream 

 and retarding the flow. 



I propose to criticise in detail the departmental mode of 

 dealing with the problem, and also various statements made 

 at the trial by the departmental witnesses, and which I 

 conceive to be erroneous and unscientific. 



The first noteworthy point is the serious error that 

 occurred in determining the high flood level of 1852. This 

 was at the time of constructing the works fixed at 16.53 feet 

 above datum, but on the trial commencing, the old value was 

 abandoned and 19.85 substituted. The ease with which 

 evidence was obtained for this latter value,, leads to the con- 

 clusion that but little care was taken at the earlier date to 

 obtain a reliable height. Further, it is to be noted that 

 the flood mark of 1852 was well known at Collins' Mill, \\ 

 miles higher up the river, and that a calculation based upon 

 this and the 16.53 flood mark, leads to a discharge of 

 enormous magnitude, many times greater than the part of 

 the valley lower down could possibly cany away without 

 the water rising to a level far higher than 16.53. In view 

 of the accessible and highly reliable flood mark at Collins' 

 Mill, the 16.53 flood level is physically impossible. Had the 

 above-mentioned calculation been made when the works 

 were being first laid out, a most serious error would have 

 been detected. 



Next it was reiterated that, however the case might be with 

 a 19.85 feet flood, that the railway works provided ample 

 waterway for a 16.53 feet one. Now I would most 

 emphatically endorse Mr. Culcheth's opinion, that it is im- 

 possible to determine waterway by reference to high flood 

 mark alone. It is absolutely necessary that discharge should 

 be also determined, and this it seems was never ascertained 

 by the officers of the department. Calculating the discharge 



K 



