RIVER CONSERVATION.

Temuka Leader, Issue 2934, 18 February 1896, Page 3

RIVER CONSERVATION.

Tho conservation works recently carried out at the main bridge crossing the Opihi river have now stood a more than reasonable test, and must bo regarded as an important and successful work. To thoroughly understand the value of tho work one must recall tho position of affairs some years ago. Tho Opihi was originally spanned by a bridge about 800 feet long, tho approach to which on the southern side was by a fairly good track through tho riverbed. At that time there were largo flax-grown islands, as they were called, in tho riverbed, which served to keep tho main current in position on the north bank, and tho track already referred to was only at brief intervals impassable through floods. Canterbury streams are proverbially erratic, and suddenly tho main stream of water made a break for tho south, aud threatened tho bank with such violence that it was deemed advisable to remove tho Arowhenua Hotel from its position at tho south-west approach to a more secure location on the south east side of tho road, and at a greater distance from tho river. That this was a wise step was shown shortly afterwards by tho scouring away of a portion of tho former site. It was then deemed advisable by tho local bodies interested, although a good deal of opposition was maiio to the proposal, to

span the entire riverbed with a budge, and some 1100 feet were added to the old structure, which was at the same time strengthened. The bridge throughout has beon a source of considerable expense in the matter of repairs, and when some two years ago the newer portion had to have a practically new superstructure and there loomed in the distance the probability that the older portion would have to be rebuilt, the engineers of the council, Messrs Meason and Maahant, intimated that they had a scheme in view for confining the river, which, if carried out successfully, would save the expense of rebuilding the old bridge and a heavy recurring item for repairs. The scheme was approved, and the river has now been confined to the width of the newer portion of the bridge in the following manner:—From the northern extremity of the newer portion of the bridge an embankment has been erected, trending in a north-westerly direction to a clay cliff or bank near the old Arowhenua bush. This embankment is some 720 yards long, of an average height of 10ft, Gft wide on top and about 24ft at the base. On the riverside a wide trench has been excavated and in this, foßowiug the line of the embankment, a very substantial fence has been erected. The fence is built of willow posts about 4in in diameter aud 12ft long, sunk about 3fb apart, and “strutted” with similar posts about 14ft long, each two being securely lashed with steel wire. About every six yards a railway iron pile has been driven to given to give additional stability, and upon the posts so erected, 20 wires, the lower five of No. 4 galvanised stranded steel wire, the remainder of No. 6 plain steel wire, have been stapled aud strained to heavy posts, 10 x 6, bolted to iron piles, and doubly stayed with pieces of 6x 4. The embankment has diverted the river at the top, and water flowing along the trench feeds the willows, which are now growing vigorously. To prevent scour there have been placed between the fence and the embankment twenty-five gorse stops. These stops are composed of bundles of gorse placed in cradles of 12 willow posts, tae whole lashed with wire, and weighed with shingle. On the face of the embankment gorse has also been imbedded. As an additional protection willow bough work has been carried out in the front of the fence. In the stream willow trees of considerable size have been floated, and kept in position by wire lashings attached to the piles of the fence and stakes. As a result, the flow of water along the whole fence is deadened, and scour prevented. The work is secured from trespass of stock from the north side by a substantial standard and wire fence. The work was carried out by the contractors, Messrs Sherratt & Co., with considerable difficulty, owing to the number of freshes in the river, but that it is a substantial one is seen by the debris on the fence, which shows that it has withstood a flood running almost up to the top wires. At first it appeared that the north stream as diverted would make for the southern branch and damage the land there. As a matter of fact it did so for a time, but there has now been formed a shingle embankment, which is protecting the south bank, and it is evident that the tendency of the stream is to flow very nearly in the centre of the bridge. In course of time the old bridge can be dismantled, and a track through the riverbed will serve as an approach to the new bridge, and thus a heavy item of expj. diture will be done away with. The work has been carried out at an expense of some £SOO, aud it appears good value in more ways than one for the money. During its construction Mr James Radford acted as clerk of the works, aud doubtless his previous experience in similar work at Parcora was of value. The council contemplate adopting a somewhat similar plan at the Temuka river, and the old bridge will be shortened and lowered.