E.—7

2

fine silt and sand were carried by this water and spread over the upper half of the island, in some places to a depth of many feet; most of the fences were swept away ; ditches used for draining the farms were filled up, and roads destroyed ; houses were inundated to the height of several feet, and some destroyed. After the flood had commenced to subside, the water flowed off the island into the Koau branch, causing other breaches to be cut where it fell over the left bank into that branch at a lower level, continuing to do so till such time as the Inch Clutha Road and River Board were able to construct stopbanks to arrest it. To a less extent the same thing happened on the left banks of the Matau, the floods inundating the land as far as Stirling, flowing back into the Matau, near Stirling bridge, and over the Kaitangata swamps ; but the mainland does not appear to have suffered damage to the same extent as the island. The railway sustained damage to a considerable extent'—part of the flood openings, some culverts and cattle stops, and the embankment beyond the railway station for a length of 15 chains, being washed away. A part of the high embankment between the bridge and the flood opening was also damaged, and narrowly escaped being destroyed. The suspension road bridge at the town had the centre piers scoured out, the wire ropes being cut in order to clear the river of the wreck. All road bridges, from Balclutha to the lakes, were destroyed with the exception of the Victoria bridge and the Kawarau, and the Cromwell and Bendigo bridges over the Clutha. Different opinions were elicited from witnesses as to the nature of the damage to the land from the silt deposited by the floods. In some places there was more sand mixed with the silt than in others ; and the greater the quantity of sand the more permanent would be the injury to the land from this deposit; but it was acknowledged by several farmers that, after an interval of two or more years, the deposit of silt would become fertile soil and yield good crops and grass. Where that is the case there will be no permanent damage done to the land from this cause. Previous floods had inundated the land in a similar manner, and deposited silt on it; the whole of this land, which is exceedingly fertile, no doubt owing its existence to the deposits of a succession of floods. 2nd. All the witnesses were of opinion that the flood of 1878 was the highest which had occurred since the country was settled. The extent to which this flood rose above those of former years was variously estimated at from 20 inches to 2 feet in and about the town. One witness thought the flood of 1866 was higher in the lower part of the Matau, which he attributed to the bursting of the banks during the flood of 1878 by which the water was relieved and subsided. We think that all the evidence went to show that the flood of 1878 was considerably higher than any previously observed. At Clyde it rose 17£ feet above the highest known flood mark, and the fact that nearly all the bridges were destroyed seems sufficient evidence to prove that the flood of 1878 rose above any previously known flood mark. With regard to the Clutha island, there was evidence given that previous floods had covered the land to nearly the same extent, but that, as the water on these occasions had risen over the island from the lower branch of the Koau, the same amount of damage had not been caused. 3rd. It is our opinion that the existence of the railway works had no appreciable influence in aggravating the damage to the township of Balclutha. This damage was caused by the overflow of the river at the bend above the town ; and it does not seem possible, considering the inclination and velocity of the flood, that the railway embankments should influence the surface of the water nearly a mile above them. Every previous great flood had inundated the site of the town and the isthmus between it and the hills; but in former times the ground had been protected by flax, scrub, and tussock, and on this occasion the scouring out of holes had originated where the ground was stripped of its covering of vegetation in streets and side ditches. Any damage occasioned by submergence was due to the greater height of this flood. In considering the question whether the railway works had any influence in aggravating the damage to the Clutha Island and the land on the left bank of the Matau, it is necessary to have a correct idea of the condition of the two channels of the Matau and Koau before the occurrence of the flood. The Matau branch is exceedingly crooked compared to the Koau, and is nearly 6 miles longer, the fall to the sea being the same in both. As a consequence of its greater length, the slope of the surface of the water in the Matau must be flatter than it is in the Koau. This would cause the current to be stronger in the latter, which would have the effect of deepening and widening the channel. This was actually the case, and the Koau, with a straighter and shorter course, used to carry the largest streams in times of heavy flood. The water, flowing over the low point of land called the Ferry, flat and over the neck of land between the town and the hills, would augment still more the volume of the Koau branch. It is shown, by levels taken on any line at right angles to the fall of the country, that-the surface of the Matau is higher than that of the Koau, and this is proved conclusively from the circumstance that, with the exception of four, all the breaches in the banks of the Matau were caused by water flowing on to the island, while all the breaches in the banks.of the Koau were caused by the same water flowing off the island into the river. This difference was probably less before the Matau had received its present great increase of water, but evidence was given that floods in the Koau river had the effect of sweeping across the island and breaking the banks, as occurred on this occasion from the flood in the Matau. The entrance of the Matau was formerly narrow, and there was a small island in the middle of it. During the flood of 1866, this island was partially washed out and the mouth of the Matau widened. The narrow entrance to the Matau, and the wide and deep entrance to the Koau had, previously to 1878, prevented the floods from forcing their way into the Matau. After the flood of 1878 had subsided, it was found that the little island had disappeared, and had given place to a wide and deep channel, while the entrance to the Koau, on the contrary, had become narrow and shallowed. It was given in evidence that, during the height of the flood, a bar of shingle and silt was formed across the mouth of the Koau, with only a shallow depth of water on it, which afterwards was partially removed by the current. Several witnesses distinctly asserted that the part of the Koau immediately south of the town, from its mouth to the railway station, was stagnant for three days during the height of the flood, and they attributed this state of things to the great flow of water coming over the isthmus from the river above the town.