E.—7

THE FLOODS IN THE CLUTHA RIVER. (REPORT OF THE COMMISSION ON)

Presented to both Houses of the Ge?ieral Assembly by Command of His Excellency.

The Commissioners to the Hon. the Minister for Public Works. Sir,— Dunedin, May, 1880. Acting under your letter of instructions dated the 29th January, 1880, we proceeded to the Clutha District on. the 12th April and examined the town of Balclutha and the island of Inch Clutha, with the object of ascertaining the nature and extent of the damage caused by the flood of September, 1878; and in this we were assisted by the plans and reports on the same subject, prepared by Mr. H. P. Higginson and the Public Works Department shortly after the occurrence of the flood. We also took evidence from the settlers as to the extent of the damage suffered by them, and their opinion on the causes of it ; we examined the railway bridge and embankments, the breaches made in the banks of the island and in the isthmus above the town, and the present condition of the river, due attention being directed to the nature of the damage sustained by the island and the town ; we also examined the works, in course of construction by the Government, intended to protect the town, the railway station, and railway embankments. After duly considering the evidence given us by the settlers, and founding our judgment on it and our own observations, we have the honor to submit the following report arranged in the order in which the instructions from you were issued to us, which were as follows : — Ist. As to the causes and extent of the floods in the lower Clutha valley, and the nature and extent of damage therefrom, more particularly with reference to the floods of September, 1878. 2nd. As to whether the flood of 1878 was higher than any previously recorded, and if so, to what extent. 3rd. As to whether the damage to the township of Balclutha or the districts adjoining the island of Inch Clutha was aggravated by the existence of the Railway works in the vieinit}'. 4th. As to the character of the various works now in progress, their probable usefulness and effect, and the various means for permanently protecting the township of Balclutha, the railway, and Inch Clutha, and adjoining districts from similar damage in future, together with an estimate of the cost of the necessary works. Ist. The causes of the flood of September, 1878, were the melting of the winter snow on the western mountains, accompanied by a warm rain from the westward. The weather at the time was fine at Balclutha, but intelligence of the rising flood was sent from stations higher up the river by telegraph. The flood reached its greatest height on Monday, the 30th September, but on the previous Sunday the river had already overflowed its banks above Balclutha, covering the peninsula between the town and the hills with a stream represented as over 20 chains wide, 4 feet deep. The water flowed across the town and down the streets, scouring out large holes in them. The flow was checked by the railway embankments for a short time, the water accumulating slightly from this cause ; but upon the railway embankments giving way, the water subsided about 4 inches, but gradually rose again until the culmination of the flood on the next day. During the continuance of the flood a great deal of the land was washed away from the banks of the river at the bend above the town. It was soon noticed that an unusual volume of the flood was flowing down the Matau Branch, and this appears to have caused most of the damage to the island and the land on both banks of the Matau. From levels taken by Mr. H. P. Higginson, it appears that the banks of the Matau are higher than those of the Koau. The former branch is exceedingly crooked, its course being about six miles longer than the Koau, measuring from the railway bridge to the sea. The banks of both branches are much higher than the centre of the island, and the land has an inclination generally from the Matau towards the Koau, and also from its upper end at Balclutha towards the sea. On the left bank of the Matau the country has a general fall towards Stirling and Kaitangata. The consequence of these features of the island was, that when the flood rose to the height of the banks ml the Matau branch, the water rushed over all the low places, making breaches in the soft earth of which they are composed, extending to the low ground immediately behind, thus opening channels for large streams of water to flow in upon the island. In places the banks were cut away by the strong current until lower ground was exposed, when the same result followed. Vast quantities of water then flowed over the island, taking a course towards the Koau branch, and also towards the sea. Quantities of I—F. 7.

1880. NEW ZEALAND.