Floods on the River Bamvon. 85 



marks, obtained long after the water has subsided (which 

 marks may have been caused at various times during the 

 flood), form the only data, the case becomes very complicated. 

 The levels of the actual Hood, as well as can be ascertained, 

 are shown in the accompanying diagram by black lines, the 

 shaded line representing the midstream section. 



8. The volume of water flowing down the river during the 

 flood of 1880 is found by the author to have been as follows : 

 — At two p.m. on Sunday, 12th September, when it is said 

 the flood level at the mills reached its highest, probably a 

 less quantity than 05,000 cubic feet per second was flowing 

 off. The level at the mills is said to have remained constant 

 till five p.m., when it is calculated the quantity of water 

 coming clown the Barwon was 09,000 cubic feet per secpnd 

 — 07,000 under the iron bridge and 2000 over the Colac-road ; 

 this was the quantity flowing through the railway bridges at 

 five p.m. It is said that the flood level at the mills fell after 

 five p.m.; but it must have gone down very slowly, since the 

 next morning it had decreased nine inches only; it is also said 

 that the flood some miles up the river, as well as at the gorge, 

 one and a-half miles below the railway embankment, was 

 not at its greatest height till about eleven p.m. All this time 

 the bank must have gone on cutting away ; and the author 

 estimates that 000 square feet of waterway were added during 

 the six hours from five to eleven p.m., which would have de- 

 noted a largely increased discharge, but for the fact of the 

 water level above the embankment falling ; this in turn gave 

 a larger difference of level at the iron bridge, allowing the 

 increased volume of flood water to come down the river 

 without raising the level on the upper side of that bridge. 

 By equating the quantities, it is calculated that about 2000 

 cubic feet per second was the additional quantity of water 

 flowing down the Barwon at eleven p.m., making the total 

 discharge then 71,000 cubic feet per second. 



9. Some water would also without doubt be coming down 

 the Waurn Ponds Creek, though it does not seem to have 

 been observed. It may safely be assumed that it was 

 being carried off by the breach in the railway embankment 

 (70 to 90 feet in length) which had occurred near what 

 is called the Marsh alltown crossing, about half a mile south 

 of the Waurn Ponds bridge. As, however, this water 

 would have to pass through the gorge (C.S. No. 1) one and 

 a-half miles below the railway, it is necessary to form some 

 estimate of the quantity. The area drained by the creek being 



