16 Embankment above Prince's Bridge. 



mile, and that at a time when the St. Kilda Road was 

 acting as a bye-wash, and allowing more than twice the 

 quantity of water to flow over it that passed under Prince's 

 Bridge. By reference to the flood-levels taken at the time, 

 I find that the sectional area of the water flowing under 

 Prince's Bridge and through the cattle arch amounted at 

 the highest to about 1,700 square feet (this section is 

 between the level of the falls and the highest flood-level at 

 the bridge.) Whilst the sectional area of the flood-waters 

 flowing over the then depression in the St. Kilda Road, 

 between the southern approach of Prince's bridge and the 

 old military barracks, amounted to over 3,500 square feet. 



It is, therefore, a waste of time to debate for a monent 

 whether the bridge is a barrier to the floods or not ; from 

 these figures the veriest tyro in hydraulic engineering must 

 know, that to stop the relieving action of a bye wash or 

 outlet for the flood-waters, by an embankment of earth is a 

 most dangerous experiment, especially when the narrow 

 spans of Prince's Bridge, and the cattle arch are taken into 

 consideration, and compared with the length of the bye- 

 wash alluded to (820 ft.) 



If any argument were necessary to show that the area 

 under Prince's Bridge is too limited for flood-waters, it 

 would be found in the fact, that whilst the height of the 

 flood was 15-17 feet at the bridge, it was only 13.10 

 feet on the upper side of the Falls, and 11 25 on 

 the lower side ; the falls being about 28 chains only from 

 the bridge. This plainly showed that notwithstanding the 

 barrier at the Falls, the flood- water escaped over it, and the 

 adjacent ground so easily, as to reduce the surface level of 

 the water 2 7 feet lower than at the bridge. 



Subsequent to my mentioning to the Hon. Mr. Casey 

 about the embankment, that gentleman informed me that 

 since the great flood in '63, the Falls had been lowered, and 

 that no damage from floods need now be apprehended, as 

 there had been a greater rainfall since that date, and that 

 the flood-waters had escaped without approaching anyway 

 near to their former level. 



In reply, I admitted that lowering the Falls was a step 

 in the right direction ; but I took exception to the state- 

 ment that there had been a greater rainfall than that in 

 December, 1863. That it might have been greater in some 

 locality of limited area I was not prepared to dispute ; but 

 that to imagine there had been a greater rainfall over the 



