THE RECENT FLOODS FLOOD DAMAGE IN BRUCE.

Otago Daily Times, Issue 18851, 2 May 1923, Page 4

THE RECENT FLOODS

FLOOD DAMAGE IN BRUCE.

STATEMENT BY MR MXURDIE

REPLY TO ADVERSE CRITICISM. The city engineer (Mr W. D. R. M'Curdle) haS'been requested to comment on various criticisms which have appeared in the Otago Daily Times during the past 10 days concerning flood matters. His comments are appended: The Kaikorai Valley sower was not allowed to discharge through the tunnel during the flood. When I inquired about it on Sunday morning it had already been turned off according to standing orders, and it was discharging into the Kaikorai stream. .The dynamiting of the foreshore conduit was' ordered the moment the conduit was reported to be surcharged. Some months previously the removal of tho flood-gate at its-outlet had been ordered because it would have been a great obstruction to flowing water. The quarry dynamiters, also the Harbour Board organisation, and the organisation of contractor M’Lennan were called in to relievo this conduit with dynamite and pick and shovel. Hearty thanks are due to Mr Wilkie, Harbour Board engineer, also to Mr M’Lennan. This conduit was completed before the council took over the Drainage Board’s work. A half-empty sower is said to have been discovered on the Flat during the flood. There were no half-empty sewers anywhere on the Flat, A connection has recently been made at Bay View road between tho sewer system and. the storm-water system whereby tho pumps may be made to take the storm-water from the Flat up to thencapacity, and, when the pumps all fail, as happened, shortly after the connection was made, all water carried by the sewers may be passed to the harbour. This Bay View road connection was most carefully watched during the whole development of the flood, storm-water being passed to tho pumps up to the limit. There came a 'stage,' however, when the functioning of the closets on the Flat had to be attended to. This necessi tatod an ’adjustment that brought about a lowering of the water in the sewers at the expense of a slight delay in tho removal of tho flood water. This relief of the closets is the astounding discovery which, is said to have acted on the spectators something like electricity. The water had then been lowered in the sewers only a few inches. The pumps stood up to their work all through the flood, and reflected much credit on the engineer in charge. Had any calamity caused the stoppage of the pumps, all water coming to them would have been passed to the harbour as before, but at a much accelerated rate owing to the dynamiting of the foreshore conduit. The Wilkie road sewer ‘is blamed "for flooding Kensington and neighbourhood by blowing a cover off in King Edward road. Had it not found relief in that way it would probably have burst about Lambert’s tile works, as may be seen by the cracks in the brickwork of the sewer above the surface of the ground. The failure of the railway flume at Burnside caused tho flood water from the Concord catchment of the Kaikorai Valley system to pour into Caversham through the ’ now railway tunnel. This catchment is between 500 and 400 acres in extent—mostly high ground—-and would furnish enough water "to cause a flood on the Flat without any local rain. The rainfall on the high ground, as carefully registered from time to time, during the worst 24 hours of the flood, was 10.7 in. The Forbury road conduit is designed to remove 2in in 24 hours When, therefore, our own 10.7 in, backed up by the. railway tunnel flow, arrived- at _Forbury Corner inlet it passed over the inlet as if it did not exist, in spite of all efforts of the man on duty with the rake keeping the opening clear. Hence tho Flat was flooded to an extent that one hopes will never occur again, not even in a hundred years It is suggested that the flood water should have been removed from the Flat much more quickly. When it is considered, however, that the Forbury conduit,, which was built to protect the Flat from the hill water, is designed for two inches of rainfall in 24 hours, and that 10.7 inches fell on some of tho high ground, it is at once seen that 8.7 inches must have got to the Flat on top of the Bin .or 9in falling directly on the Flat itself. On tho top of all this comes the water through the tunnel, which would be about enough in itself to cover the Flat 6in deep. ’ Hence, we have a flood on the Flat about 18in. Tho exact areas of all the hills of Mornington, Caversham, Green Island, and Taieri County (hat poured their waters on to the Flat are not yet available. Taking the total flood on tho Flat at 18in. and a system designed to remove 2in in 24 hours, it will be seen that the water was got rid of pretty promptly. To the question. Can such flooding be prevented in the future, the answer' is in tho affirmative. Details of ways and means are for (ho Board and Council, but not through the newspapers. This" applies to the Flat and St. Andrew street. The Leith across the reclaimed land from Fqrth street to the harbour is a Harbour Board problem. Deplorable damage has been done by the overflowing of the Leith outside the City Council’s length, which _is from _ Leith street to Forth street. This system is built on a system I saw practised on soino of the torrential 'streams in Eastern France, as far as the bottom and side are concerned. Outside the channel the cradge bank system I saw practised when studying the drainage of flats in the Fenn country in England comes into play—that is to say, ■the main channel is built to take the highest known flood—but in a young country like Otago whose records go back to 1851 only, bigger floods than those recorded may take place. Ready to receive any such flood, cradge banks were raised where necessary to take a flood about sft above the level of the walls. Consequently there was no overflow in the council's section till the water reached Forth street, where the tide begins to act. The turbulence of the water on this section has been noted. The standing waves in the. centre at some of the Tails stood 'about Bft above the level of the walls before the channel was quite full. It was an aweinspiring sight, but the flow was under complete control all the way. The velocity dpwn this section was enough to carry the drifting boulders and shingle down to near Harbour terrace bridge and below it. A concrete bottom is suggested to do away with the turbulence and the standing waves. Concrete would be very temporary. The thundering of the boulders would quickly break it up. In a violent torrent like this another form of bottom is used, when a bottom is used at all. If any pools are left for the delight of the children a standing wave will form at every one of them. Considerable quantities of mud, sand, and gravel found their way into the sewer system as suggested in the columns of tho Otago Daily Times. A quantity is thus delivered into the system in every flood, always in proportion to the flood. The state of the streets gives some idea of the state of some of the sowers until they giro cleaned out again. Your readers may Slot bo aware that tho sewerage system was designed and executed to tho cost of about £400,000 before the present administration tool; it oVer. It has been taken over ns a going concern, and improved and extended a-s funds have, allowed.

Among: the recent troubles was the failure of all the three sources of water supply for the city. The 12in main from, the Sullivan dam wag removed by the torrent which came down Nichol’s Creek, -wiping out the bridge over the creek nijd part of the road. The 12in main front Ross Creek, under .the bed of the Leith was broken, and the Silverstream/ race was put out of action by slips from above and below. Fortunately these things, came on one after the other, and svs no time was lost in making them good one after the other, it was only during Saturday ‘last that there was any inconvenience in town or on the Flat. The •Southern Reservoir would have’tended the city over all trouble, but, being empty for excavation purposes, it was not available.

You will doubtless be glad to hear that of alb the works designed and .carried out by the present administration, from. Waitati to Waipori, and from Silver Peaks to the sea, not one has failed or ceased to function all through this historic flood. I say this in all humility. When the whole drama is carefully examined it will be found that neither the board nor the council will require to apologise or pay damages for anything which ha* been done or left undone before, during, or since the great crisis.

The loss and suffering of those in the flooded areas call for heartfelt syapathy.

THOUSANDS OF POUNDS’ .WORTH. GOVERNMENT ASKED TO ASSIST. The following report bearing on flood damage was presented to yesterday’s meeting 'of the Bruce County Council by tho inspector (Mr J. H. Bateman): — • Matau and Inch Clutha Ridings.—Very little damage has. beeh done in these ridings, and about £lo will put things in order again. Balmoral No. 1 Riding.—l have not had time to visit this riding, but so far no report of any damage has been received. Balmoral No. 2 Riding.—This riding has not been visited yet, but I have received word that therms a washout on the embankment between Moir’s and North Balclutha, several small washouts on the Riverside rood, the approaches to tho Blackburn bridge damaged, also deep ruts in some roads and metal badly scoured in places. Crichton Riding.—A stone culvert washed out at Tweed's, Lovell’s Flat, and is being replaced by one of concrete pipes. A stone culvert near M’Crostie’s homestead has been damaged anti will have to bo renewed with concrete pipes when these can be taken down by rail. One wall in the Fraser's Creek bridge at El Hot vale bus been damaged, and will be repaired as soon as possible. Kaitangata Riding.—A culvert washed out in the deep embankment below OockcriH’s, and is being replaced by 2ft concrete pipes; about 300yds of material will be required to make up the roadway. There are sonie bad slips on the same road in this riding, and these will bo attended to as soon as possible. A washout occurred at (he Rooks on the Wangaloa road, one also on the school road. The culverts in these places are not damaged, .but at Dead Creek the double culvert has blown clean out, leaving a gap in the road 40ft wide and 10ft deep. A'new culvert is also required near Caird’s mine, and tho stone walls of a small bridge at Kain’s have been partly washed out. Glenledi Riding.—The clay and metal have been washed away from the pipes at Genny’s Bush, and a larger culvert is required at the foot of Grange Hill. The metal has been badly scoured on the school flat. I expect that £SO will cover the damage done in this riding. Waihola Riding.—This riding has had a bad time. Morgan’s bridge has washed out completely, piles and all, leaving a gap a chain wide, and as this is on a main road with no other outlet, a temporary bridge is being erected a little further up the creek. A gap has been made in -Sawmill road, three quarters of a chain wide. The north abutment and wing walls at Akatore Creek bridge have washed out,- and the end of the bridge is down in the river. A longer span will be required to bring tho end of tho bridge put to better ground. Coutts’ Gully road is blocked by slips and a small bridge washed, away. A big slip is • down on the road above' the manse at Waihola. and the road between Scott’s Hill, and Whalan’s is completely blocked •by several big slips. This portion oi road will hardly be open for traffic this winter. There are seven small slips on the main road between Titri and tho ferry bridge. Clarendon Riding.—l have not visited this riding, but I understand the damage is not extensive.-

Tokopiairiro Riding.—*A brick cuvlcrt has partly washed out at Tokoiti, and is being replaced by 3ft concrete pipes. The northern approach to Salmond’s Creek footbridge has been washed away, the three stone retaining walls at Mount Steep are gone, there are two big and three small slips at Mount Steep, and one over a chain long and seven feet deep at Louden’s Gully, also a long , slip near Akatore schoolhouse. A big slip on Coal Gully road above Woodhead's, and one on Cock bum’s road, Elliotvale.

Mount Stuart Riding.—The damage in this riding is -very heavy. Two bridges have been washed away and a portion of the stone arch in Manuka Gorge; a washout at Callanan’s road is over a chain long and from 4ft to 15ft deep. A large slip above the Manuka Creek School blocked tho road. Both approaches to Clymers and the western portion to Glenore bridge were washed out. The footbridge at Hanley’s ford and tho embankment washed away. The footbridge at Crofthead, Lovell’s Flat, damaged, and a culvert washed out on the Roxburgh Estate road rear the sheep dip. Several miles of tho Lawrence road is badly scoured and the metal washed off in places. I have not heard of any further damage in this riding so far. Traffic is able to get through to Lawrence by going over Bullocky Hill. This is. not by any means a good road, but if if is re-formed I am afraid it would become impossible for traffic to get through unless a large amount is spent in gravelling. There are a number of roads throughout the county that are badly scoured, and a considerable quantity of metal and gravel will be required to put them in order. There are sufficient concrete pipes of all sizers in stock to meet all requirements in connection with the flood damage. It is impossible to make anything like an accurate estimate of the damage done in tho county, but ’ several thousand pounds will bo required to put the roads and bridges in their former order. Cr Sheat, in referring to tho damage done in his riding (Mount Stuart), said that it was worse than what the inspector so far knew. This applied particularly to the Gorge. Assistance would have to be obtained from the Government or somewhere else; tho riding could not stand it.

, The Chairman (Cr Bell) said that his riding had probably had the worst time of the lot. There were 14 slips on the Waipori road, and it was difficult to say when it would.be open for traffic. . On tho motion of Cr Clark, seconded by Cr Scott, it was decided to draw up an estimate of the damage done and to forward to the Government an application for assistance in the cost of carrying out repairs. Cr Russell referred to the good work "done 'bv many settlers who had come to the assistance of the county by carrying out minor repairs. Other councillors also spoke commending the people, and an appreciatory motion was passed.'