OTAGO HARBOR WORKS

Evening Star, Issue 18280, 21 May 1923, Page 2

OTAGO HARBOR WORKS

FORESHORE IMPROVEMENTS. EFFECTS OF THE FLOODS. LEITH BED NEEDS SYSTEM OF CONTROL. In a tour ol the Pelichet Bay-Black Jack’s Point area this morning a/ Star’ reporter saw things that nro of interest to all who havo the interests of thej city at heart. . Standing on the Harbor terrace bridge a view was obtained of a stretch of tho Leith that was partially choked by the floods. Thousands of tons of stones (big and little) and gravel camei_ down the stream and! fanned banks in it. Men in the service of tho Harbor Board are. now clearing away this debris. On one side it is packed up sft or 6ft high just below tho Harbor terrace bridge, and 1 for a length of approximately 800 ft the stuff is lying in quantity—that is to say, from Forth street bridge 'to the railway bridge. This work is urgent. Mr Wilkie evidently deems it wise to get at the trouble whilst the stream is relatively low, for he has taken off tho hands from the Sunshine and Black Jack’s quarries and put them to the Leith job, a steam crane being at their service to hoist out the stuff and deposit it in a depression at the northern back of the canal wall. The clearance will give the Leith, a free nm at that part if more heavy rain comes. When the stream falls a little more it may be possible to use motor trucks in the bed and run out the stones at express speed. The position in regard to the Leith calls for something more than this clearing that is now going on. The City Corporation made the channel from the upper end as far as tho Forth street bridge, and this portion is on a somewhat steep grade. From thence to the outlet tho construction of the channel was by the Harbor Board, on a much more' level grade. _ This fact is important, because the action of the Loith during the floods seems to indicate that Nature is trying to make one grade of it by depositing debris at the junction, and as Nature partially choked tho bed in a Hood of three or four days’ duration it is probable that it would make a devastat- ! ing block should another flood come and last longer. Engineers may be left to deal with that problem. What strikes the layman is that it is about time to set up a system of control in the upper reaches of the Leith—a system that would forbid encroachments, and in that and other ways stop at least some of the erosion that lets so much stuff come down the stream when it is running high. Is not this worth thinking about? At the time of what is called the second flood a cut was made through the road to Black Jack's Point in order to relieve the Lake Logan area of a lot of water. The box culvert then put in is to bo allowed to remain. It may do good work again. From the time of the first flood (April 22) the pumping of silt by tho Vulcan was diverted from the estuary to Lake Logan, and this is still going on, with the result that the solid level of the .area that was once a lake is appreciably higher—a fact that will be appreciated by those, of our citizens who wish the exhibition to be on that reclamation. Mr Wilkie says that the chief reason for stopping tho delivery of harbor spoil into tho estuary was that the flood swept out into tho bay a great lot of stone that had been deposited in the gap of the Black Jack’s Point wall. Prior to the flood this gap was built up to half-tide level, and was beginning to operate as a stopper to the mouth of the estuary. When the flood washed out tho gap to something like its previous depth it was no use to pump more stuff into the estuary—it would be shot out at once, as from an uncorked bottle—so tho first work at this spot is to fill up the gap again, and then the reclamation of tho estuary by the pumping process can be recommenced. Tho material that was used to fill np the gap in the wall came from the quarrying operations at Black Jack’s Point, and it is from the same place that stone will be carried to once more use at the gap. Most of the stone that is blasted away at tho point is ferried across the Victoria Channel to the halftide wall, but there is plenty to spare for the gap. The reclamation of the estuary is making steady advance. Just below' the boat harbor the height is pretty well up to the permanent level. The floods caused some scour in the now narrow stream that runs through the estuary, but the loss by this scour was really very light hy comparison with what it might have' been. Tho restraining influence in operation was the scrub fence. Mr Wilkie says that much credit is duo to Mr T. Leo for the way ho has made and looked after this scrub fence. It looks frail as a bulwark, but it has saved the situation, and it is satisfactory to learn that notwithstanding the perpetual contact of water the scrub is not rotting. When tho w r ork of cutting away the tip of Black Jack’s Point was figured out, the engineer’s estimate was that 13,000 yards would have to be quarried, out. As seen now, about three-quarters of the work is done. Tho railway lino now slands quite clear. The stone that is still to he taken out seems to be quite as hard as that which lias been removed, if not harder. The cost represents a stiff price to pay for the straightening of the railway, but it will ho a good job, and the cost is not all a debit, because the bulk of tho quarried stone has been very handy for raising the half-tide wall —n work for which it would otherwise have been necessary to bring tho stone from afar. It is noted that the fresh in tho upper harbor caused by the floods did not damage tho half-tide wall nor move the recently-deposited material. On the way back onr reporter bad a look at the Leith canal works at the