THE MOLYNEUX RIVER

Otago Daily Times, Issue 17936, 15 May 1920, Page 71

THE MOLYNEUX RIVER

FLOODS AlO) THEIR CAUSES

PROPOSED PROTECTIVE MEASURES.

COST ESTIMATED AT £166,000.

RIVERS 1 COMMISSION'S REPORT

The result of the investigations of tJw Rivera Commission, whioh collected evidence of a very comprehensive nature in the early part of last year into the causes of the silting up and flooding of the Molvneux Raver in its lower reaches, is the subject of a very lengthy report. The commission consisted of Mr IT. W. Furkert (inspecting engineer Publio Works Department, chairman) and Messrs F. C. Hay and Ashley J. Hunter. Tho report states: The Clutha River, with its tributaries, drains country exhibiting most diverse characteristics. The waters from its 2749 square milea of drainage area pass through Lakes Wakatipu. Wanaka, and Hawea, and consequently violent freshets are to a large extent steadied or prevented from affecting the countrv below the lakes; Dut, on the other hand, when sustained and violent rain or melting snow has raised the lakes considerably above their normal level, the river below continues to ran high, frequently for many week 3, while this surplus water is draining away The characteristics of the flow of the lower river are therefore different from those of (the great majority of New Zealand rivers, in that as a _ rule floods rise slowly ,giving ample warning, and, having risen, remain up frequently for days, and take a long time to subside. This is a characteristic whioh must be seriously considered in deciding the necessary cross-sec-tion for levees and other matters. THE POMAHAKA MENACE. The country above the lakes is highly mountainous, and rain and snowfall there are extremely heavy. Below th© lakes to Balclutha there are 5072 square miles, over the greater part of which the rainfall is low, and in some places vary low; in faofc, the Clutha watershed contains the driest locality in New Zealand. Heavy floods resulting from widespread rain over this lower watershed are most unlikely, though at times any one of the tributaries is likely to be in a raging flood irrespective of the river. The total stream cross-section in the lower reaches is, however, so great tributary floods cause no trouble, except in the case of the Pomahaka, in the watershed of which the rainfall is higher 3an in the rest of the watershed below the lakes; The Pomahaka drains 800 square miles, and reaches the main river only 10 miles above Balolutha. The experience of May, 1917, shows that a flood sufficient to create widespread damage may come from a flood in this tributary, Augmented by the ordinary normal flow of tho,main stream. T.AK"TCS AND MINING AREAS. 'The character of the rocka and soil above the lakes has no effect on silting, as the lakes form reservoirs so large that all mattor in suspension entering them is precipitated, even in times of the fiercest goods. Through a large portion of its course below the lakes the river—or rather the two main rivers, the Clutha and the Kawarau, which unite at Cromwell, and whioh are from that point known as the Clutha or Molyneux—runs through what is geologically a very youthful ..gorge, in which the forces' of denudation have not yet brought the slopes to a stable angle. It is only the extremely low Tainfall that saves the precipitation into the stream of vastly incneased quantities of the extremely loose and friable schist rook which forms the greater part of the country Unfortunately, the mines operating in the watershed are almost entirely confined to beds of old and also fairly recent gravels, which have already been reduced to such shape and size as permits of their easy transportation by the stream. Nature takes long periods to reduoe the rook to gravels, and the, pouring in by the agency of man of immense quantities of gravels whioh have taken ages to produce naturally causes accelerated deposition lower down. The Pomahaka watershed is entirely different from that of the balance of the Clutha watershed, being largely rolling country, almost entirely gra<& and bushcoverea, and the amount of detritus travelling in this stream is surprisingly small. TIDAL INFLUENCE. The fall in the river is moderate. Where passing through narrow gorges the fall is steeper than ■ average, and is succeeded: usually by some miles of flatter stretches, in which ocour old gravel deposits. These steep and flatter alterations both become progressively flatter as the coast is approached, andi when the vicinity of Balclutha is reached the fall has became very slight, there being only 9ft of fall from low river level at the Balclutha traflio bridge to ordinary high water mark. The tidal influence is felt for nearly 11 miles up the Matau branch, and about seven miles up the Koau branch. Evidence was given that deep-draft schooners had navigated the Koau branch up' almost to the top of the tidal influence At the present day a flat-bottomed, shallow-draft steamer has great difficulty in traversing the same roach. This will show to what extent the shoaling-up has occurred. TOTAL WATERSHED. The following table gives approximately tho area of the various subdivisions, and also the total watershed of the river: — Sq. Miles. Lake Wakatipu ... _ 1179 LaJte Hawea 560 Lake Wanaka - ... ... 1010 Clutha River, above Clyde ... ... 46t0 Manuherikia River, above Ophir ... 802 Manuhearikia River, above Alexandra 1164 Ltndis River 405 Pomahaka River 800 Lake Wakatipu (ditto) :.. „ ... 93 Waitahuna Itiver _. ... 14-7 Waiwera River _ .„ ... 94 Puerua River „ 77 Tuakitoto Lake • ... „. 80 « Clutha River, to Balclutha ... ... 7821 Clutha liver, to Mouth 8091 (Total watershed) Lake Wtfnaka (area of lake) 70 Tuapeka River 84 Lake Hawea (ditto) 41 The watershed of the Clutha River below the lakes, before settlement took place, was covered with natural vegetation, principally tussocks, with scrub in the gullies. Owing to a variety of causes, chief among which were burning-off by the settlers and keatingoff by rabbits and other animals, lange areas are how bare; the gullies have not the help of the - roots of the scrub and vegetation to retain the loo6e material, and', consequently, whenever thunderstorms—which are somewhat prevalent in parte of the watershed—ooour, immense quantities of material are torn from the hillaid3s and carried towards or into the main stream. DENUDATION AGENCIES. The commissioners consider that the effect of interfering with the original physical character of the watershed by agricultural and physioal 'operations, including burrowing by rabbits and burning-off, has decreased the stability of the surfaco soil, and thereby enabled tho natural denuding agencies to carry increased quantities of detritus into the river and its tributaries. This increase over the natural denudation that oocurred bofore any settlement took place, and which the river was able to transport safely to the sea, would, in their opinion, be ias much as the increase due to mining operations, and therefore the settlers and tho miners are equally responsible for tho shoaling that has taken place in the vicinity of Balclutha, as far as that shoaling is due to the increaso of detritus poured into the upper readies of the river and its tributaries. * The burning of tho tussocks was done to a much greater extent in the past than is now done by the runholders, with the idea _of improving the grass. limited burning undeir strict supervision, and at the proper time of the year, may not do much harm and possibly does improve the grass, but- the commissioners aro so strongly of opinion as to tho immense amount of harm which can he done, and frequently is done, by the burning getting out of hand, that they consider the stopping of the practice of burning the tussock should bo under st.riot regulation, if not forbidden by law. That there is now not so much burning as heretofore is largely due to the fact that there is nothing loft to burn, and consequently nothing left for" tho stock to oat. or, what is more important so far as river control is concerned, thoro io nothing fo prefect the face of the country against the elements. Although within the watershed below the lakes thore was nover very much largo timber; what there was has been almostly entirely cut out, especially for mining timber. Whatever the cause of the disappearance of the native vegetation, there is no gainsaying the fact that, thf denudation from natural cause-? henceforth will be very muoh worse than in the past, and will be a very serious factor for consideration in connection with tho safeguarding of lands lower dov&

The geological cvidonoe shows plainly that a great deal of subsidence has taken place in the lower valley, and the presenco of undecayed forest below high water mark shows that subsidence has occurred within comparatively recent goological times. vV hether tliis downward movement is now going on cannot be determined with certainty, but in aJiy case the commissionara do not consider that a movomont, either upwards or downwards, is likely to ocour at a sufficiently rapid rate to justify them in making any modification of their suggested works to oope with this movement. RECORDS OF PA.ST FLOODS. Heavy floods have been recorded in 1851, 1866, 1878, 1912, 1913, 1917 (2), and 1919. Tho 1878 flood was the highest, known sine© settlement ooourred, but physical evidenco of a still greater flood wus observed by the early showing that tho water stood something like 6ft above the highest level reached by the 1878 flood, near the top of Incholutha. It is quite impossible to form any idea of how long ago this flood occurred, although there is a Maori traditions as to its ocourrenoo. Tho heights of successive floods, as recorded on the gauge on tho Balolutha traflio bridge, are as follow: — September, 1878, 16ft (flood ooourred before gauge was erected, and height was obtained inferentially). October, 1912, 12ft. March, 1913, 13ft 6in. May, 1917, <*sft 6in. September, 1917, lift 6m. January, 1919, 17ft. • The heightq °f the floods occurrihg prior to 1878 were not reoorded at the same station, because it did not exist before then. The evidence of witnesses, however. shows that at Inohclutha the 1£66 flooa was approximately 2ft below the 1878 flood. It might be imagined from the fact that the 1919 flood stood at 17ft, while that of 1878 only stood at 16ft, that the former was the greater flood: such, however, is not the case, • because at the tiroo that tho 1878 flood occurred the conditions exist-, ing at and below Balolutha wore entirely different from those obtaining at the time of the more recent floods, inasmuch as in 1878 no lerees had been constructed, and the flood waters not being confined, spread over a considerable area of country. After very careful consideration of all the facts and data at their disposal, including levels, slopes, and oross-sections at Clydovalo and Pukeawa, where little alteration in the stream has occurred, the commissioners have arrived at the conclusion that the flood discharge of the 1878 flood may bo fairly stated as not exceeding 180,000 cubio feet per seoond, while that of 1919 was about 120,000 cubic feet per second. DAMAGE CAUSED BY MINING. Tho commissioners found that mining operations of enormous magnitude in the aggregate had been carried out within the watershed of tho Clutha, tho total yardage moved being estimated at 300,000,000 cubio yards. It was not claimed that all this material had actually caused silting at or in the vicinity of Balclutha. An immense amount of it had come down the river and been swept out to sea,_ being oarried in suspension after reduction to appropriate siza Probably a still greater quantity was still lying in the sullies and sludge channels, as well as in the bottom of the main river. Probably 200,000,000 cubic yards had not yet reached the main river. Of the balance of 100,000,000 cubic yards probably 60,000,000 was lying in the bed of the river, in thickness varying from 10ft in the upper reaches to 3ft in the lower reaches, tho residue of 40,000,000 cubic yards haH been swept out to sea at an average rate of 670,000 cubio yards ner annum. The whole of this material must eventually be brought down' by successive floods, and the commissioners -wished to stress that this large amount of foreign matter could not have been sluiced into the river without upsetting the balance of Nature, and causing silting where nreviously silting had not occurred. It appeared that over £19,500,000 worth of gold had been won from the mines in tho valley of the river, and the revenue derived by the General Government, and paid to the various local authorities in whose districts the gold was won since 1877, which was the earliest date covered by the Treasury records, was £158.653, i as supplied by the accountant to the Treasury. This could not be considered as in any way representing the actual monetary -benefit to the State from the mininjg industry, which had been one of the principal foundations nf the prosperity of Otago. THE GOVERNMENT'S LIABILITY. The amount of gold being won was not sufficient to justify the commissioners recommending any contribution from that source towards the cost of remedial measures, but the General Government, having been responsible _ for the _ proclamation authorising thft deposit of mining tailings at the various tributaries, cannot escape liability to contribute towards the cost of works recommended herein. Similarly it was considered not justifiable to recommend that any direct contribution to the cost of remedial measures in the vicinity of Balclutha be derived from the land under settlement in the watershed of the Clutha above the portion referred to ip the order of reference. BALCLUTHA'S UNFORTUNATE POSITION. Both before the appointment of the commission and during its investigations, a widespread feeling lias been given expression to that the town of Balclutha should never have been built where it now stands, and that therefore the people having gone into such an unsuitable township site of their own volition are entitled to no sympathy for the troubles in which they now find themselves. While the commissioners agree that it is regrettablo that such a site should have been chosen and developed to its present stage, nevertheless they feci that as the General Government was to a certain extent to blame in the first place in cutting uip a limited number of sections on the peninsula (Balclutha), and as tho town has now an established prosperity, and has become recognised as the trading and official centre of a large and valuable district, its present existence must be recognised, and its value is suoh that it must be protected. Your commissioners have oonsidered the possibility of removing the whole of the improvements now on the peninsula (Balclutha) to higher ground, but are of opinion that the expense which would be thereby incurred, both in the actual work and in tho dislocation of business, is too great to be warranted. While the flooding of agricultural land is detrimental and .should be avoided, nevertheless if it should happen it can be j borne, and merely represents the loss of j so much money, but in tho case of a closelybuilt town suoh as Balclutha an inundation ' such as would occur in tho event of the protective works fajling would undoubtedly ; result in a loss of life in addition to a j great loss of property, and for the former reason alone very considerable expenditure on protection would be justified. Had no protective work been erected at Balclutha the risks and the actual damage to Barnego would bo considerably lessened. It is not likely that the area of land at Barnego is sufficient to justify protective works adequate to withstand the greatest flood to be anticipated, but protection against all floods is required at Balclutha, and consequently Barnego must be prejudicially affected and should receive from the town of Balclutha some assistance towards an insurance fund , of a character to be. outlined later on. If 1 tie inhabitants _ of Balclutha are not pre- I pared to pay annually towards such an in- ! su ranee fund, then thoy must be charged ' with a very considerable portion of the cost of raising the Barnego levee as high as the Balclutha levees. CHANGED CHARACTERISTICS. That the lower reaches of the river do not now possess their original characteristics was affirmed by practically every witness old enough to recollect early con. ditions. Before the mining became an important factor the river was a deep clear-running stream, with the water tho deep blue characteristic of its upper readies at present. It is now, especially in the Koau branch, full of shingle bars, always muddy, and generally much shallower than it was, say, in 1860. At that time, also, the tidal influence was felt- considerably further upstream, and drains which were j then constructed to discharge into the j river through automatic tide gates at low I water cannot now so discharge. EXISTING PROTECTIVE WORKS. A great deal of useful work has been carried out for flood protection in the past. A general description of these works is as follows: the Barnego Flat on the left bank is protected by a levee approximately parallelling the river, and connected with ! a hill at each end, the height of the levee , being generally up to within an inch o<r ! two of the height to which tho 1919 flood rose. The levee is not continuous, as > portion of the river bank is sufficiently j high to be abovo the grade of the flood re- I ferred to. On tho right bank there is n ! very strong levee extending from tho lii! ,c 1 about one mile and a-haJf above the Balclutha traffic bridge down to some com. paratively high ground in the vicinity of the Agricultural Show Grounds. The greater portion of the levee was erected j shortly after the great flood of 1878, and its top was made up to tho observed flood

marks of that flood. No allowanco was mado for tho inevitable rifling of tho flood duo to tho cutting off of tho flood overflow across tho peninsula, (Balclutha). In lator years this danger was partly radioed, and tho levee was raised 3ft, and otherwise strengthened. Hod this not boon dono a catastroplio must liavo' ooourred in 191.9. In addition to overflowing tho peninsula in and prior to 1878 an ivotivo erosion ol tho peninsula on tho western side was in progress, and simultaneously with tho construction of tho lovee in 1880 a great deal of riprap was placed in tho concave bonds, so tis to clothe tho bank from tho top to the bottom of tho river. This was so successful that erosion, which hud amounted to 50 acres betweon 1847 and 18$0, has been entirely arrested. At various times lovees liavo beeai constructed on 'Inchchvtha wherever the experience with previous floods has shown tho danger of overflow. 'lhere are on the island many mileß of them, soma being fairly high, but tho majority of moderate • dimensions. A large levee known as tho Hermitago bank, and ono or two smaller banks immediately in the vicinity of tho town, protect Stirling from tho overflowing of floods of such volume as that of 1919. In this coiineotion it may be well to remark that these levees "should protect the land, but in actual fact they were breached by both the 1917 and 1919 floods, duo to their not having been properly maintained, and rabbits having boen allowed to burrow clean through them. Tho sanio remark applies to the levees on Incholutha, which have been breached at different times. The Waitopeka Stream, which previously had joined the Puerua Stream near its confluenco with the old mouth of the Clutha River, has been diverted into tho Clutha River direct by a canal passing under tho Oatlins River branch railway into an old lagoon, and thenee into the river. A tidal gate has Been constructed at tho mouth of tho Puerua River to prevent the high tido backing up the stream and thus to improve the drainage •of the Otanoinomo Bwamp. A levee of small dimensions has been constructed near the mouth of the Waitepeka Canal referred to above, down to a point within a mile of the Koau mouth. The outlet to the Tuakitoto and Ka:tangata Lakes has been improved by'the construction of the canal connecting tho Kaitnngata Laks with the river, and also by an extension connecting the two lakes, the high water of tho Clutha being prevented from flowing through this canal back into tho lakes by the erection of tidal gates at the lower end of the canal. This protected a large area of the lakes district from Clutha flowi waters, and greatly improved the drainage. Incholutha a large portion of which ha 3 been originally swampy, was also improved by a comprehensive scheme of drainage. The total capital value of the land subject to flooding is set down at £1,192,000. FINDINGS AND RECOMMENDATIONS. Tho Commissioners met again in Dunedin on February 17, 1920, and after revisiting the salient points on the Clutha, drew up their report, with .the following findings on the' various heads in the order of reference:— CAUSES OF FLOODING. 1. To inquire into the cause or causes of the silting-up of the channel, the flooding of the adjacent lands by tho said r<ver, and erosion of its banks and the damage to the surrounding country. This is largely due to the quantity >.f debris coming down from the mining operations in the many tributaries of the river draining tho gold-bearing country, and acting as 3udge channels for the mining operations oarried on therein; also to the acceleration of natural denudation by removal by burning, agricultural, and pastoral operations of the protective covering of natural vegetation, thereby giving the river an overcharge of detritus in excess of its natural carrying capacity. The fact that the traffio bridge at Balclutha has a throttling effect upon even' small floods has assisted to aggravate tho silting-up between the town and Barnego Flat. A certain amount of silting in tho Koau and Matau branches has also been caused by the growth of willows, especially where they have lodged in mid-channel and formed the nucleus of an island. EXTENT OF THE DAMAGE. (2) To ascertain the nature and extent of tile damage done to the lands adjacent to the said river, and what area ot land is affected by such floods or erosion, or both, and whether it is practicable at reasonable expense to prevent such flooding or erosion, or both, either wholly or partially. The damage is of a maniloid nature: (1) The actual erosion of ttie banks, causing a direct loss of land. (2) Overflowing of the 'banks, earning damage to the improvements on the land and the crops being grown thereon by overflowing. Tii3 flood waters sometimes- lie on portions of the ground sufficiently long to kill tho vegetation, and in other plaoes they carry such a quantity of silt as completely covcrs the vegetation, and kills both grass and crops. The amount of damage done varies greatly with the season and consequent condition of agricultural operations, but history does not seem to show any definite flood season; of the heavy floods on record three occurred in the spring, ono in the summer, one in the autumn, and ono in the winter. Damage is also done to house property and furniture, due to floods actually invading the houses, and the value of many portions of the district for building purposes and for agricultural pursuits is depreciating, because 'the fear of floods prevents people lving therein, or prevents them from carrying out agricultural operations, wiiioh would l be jeopardised by floods to a greater extent than would mere grazing. In 1878 the flood which swept over the town of Balclutha did an enormous amount of damage. It also did great damage to the farhi lands in all parts of the flooded area. The flood of 1917 did considerable damage on the left bank of the Matau branch at Otanomomo. The flood of 1919 did immense damage to the same localities, and also in Incholutha, and but a small amount of damage in the town of Balclutha. Enormous damage in Balclutha would have been sustained had it not been for the protection afforded to the town by the works erected by the General Government about 1880, and strengthened and raised*—partly at the expense of tho Borough Council and partly at tho expense of the General Government—in 1913. . (3) The roads in the flooded area were damaged by tho metal being washed off them, and bv the deposition of silt, sometimes to great depths, over tho existing metal. (4) Railway traffic was interrupted on tho main south railway in 1878 for a considerable period. The main lino was also breached at Balclutha, and large and costlyviaducts had to bo erected in place of the banks which had been washed away. In 1919 railway traffic was interrupted for eight days. In both of these floods, and also in the flood of 1917,_ the private railway running from tho main line at Stirling to Kaitangata was breached, and the traffic interrupted for considerable periods. Interruption of tho private railway from Taratu to Lovell's Flat was also suffered. This re-* suited in tho stoppage of the coal traffic, and represents a dead loss, not only to tho companies, but to the Government, which can never be made up. The works of the South Ctago Freezing Company wtre seriously jeopardised bv the compartively moderate flood of 1919. With regard to erosion, 50 acres of land was eroded from the peninsula (Balclutha) between 1847 and 1880. The fear that the whole town would be swept away by this oauso was what prompted the Government to carry out certain protective works. In addition to building a flood protection levee on tho upper fiido of the town, the whole slope of the river from the top of tho levee to tho bottom of the river was clothed with rip-rap. This has been entirely successful. Erosions similar *to those which took place noar Balclutha have taken place in a great many of tho concave bends between the town and the sea, but in almost all cases complementary accretion has occurred on the opposite bank of tho river, so >that the ultimate area of the river bed or river channel is not materially, if any, greater than it was when the land was first settled. Though certain hardship may have boen caused to individual owners by the erosion other owners have gained by the accretion. Nevertheless, the amount oroded at any one point other than at the town docs not, in the opinion of your commissioners, warrant the carrying out of tho extensive wor>ks which would be required to prevent further erosion. If tho land between the stop-banks were the property of an organisation controlling the river then no hardship would be caused to any individual owner, and the central authority would gain in one place and lose in another, remaining substantially at it was. If erosion at any point proceeds to such a length that the levees are threatened with undermining, it would be better to purchase a strip of land iwid move them back than to attempt protection, unless there are some verv special conditions v.-lvch would warrant this latter course; being adopted. Tho commissioners consider it practicable to wholly prevent the flooding, at reasonable expenso.

RIVER CONTROL. (з) To ascertain the test method of providing for tho, control of tho said river und its tributaries so as to safeguard tho lands affected, and to provide far tho effective control and improvement of tho said river und its banks. < Tho works recommended by tho oornmiseionora consist generally of: — (и) Tho raising of the present traffic bridge at Balclutha, the strengthening of ita piers by tho sinking of another cylinder upstream, and by bracing all three together in a substantial manner. Tho ooinmisaionors consider that the erosion of tho termco under the bridge on the loft bunk should bo encouraged by ploughing tho surface when a flood is likely to occur. The character of the river ia sueli that ample warning can be obtained from stations higher up the river. Under the bridge, and along tho banks in its vicinity on the right bank, the present mordinnte growth of willows should be kept within bounds sufficient only to protect the works, so that sil ting-up in that locality during poriods of low river and moderate freshots will not be encouraged. (1>) The main levee protecting the town of Balclutha must bo raised by an average height of 6ft, at the grades shown on plans. It should be constructed of solid material, preferably a mixture of clay and rock from the hillsides, from which the original material was obtained. When the levee has been constructed to the raised height, and to tho dimensions indicated (9ft on the top, with 3 to 1 batters nt tho back, and 1£ to 1 at the front), it might with profit be dedicated as a public road after being sufficiently widened on tho top, with natural batters. Its use ns a public road would allow of subdivision for residential purposes of the land not now served by a public road, and would result in ite being constantly patrolled and maintained, and therefore no longer serving as a harbour for rabbits, as it has done in the pust, and does still to some, extent, in spite of the alleged rabbit-proof fences. In view of the fact that no maintenance to the riprap has been done for 40 years, the commissioners consider that the time has now arrived when a quantity of stone, say, 10,000 yards, should be distributed along the toe of the levee. This could best be done by tipping from barges moored at fixed distances from tho water's edge, so that tho stone is delivered exactly where required. It may be possible to place the stono by tipping it off the levee, but there is doubt a/S to whether it would roll into tho desired position. Experiments should be made by this method before the barges are constructed. (c) From the end of the raised traffic bridge a levee of similar dimensions to the levee just specified, and to the grades shown, should be carried down and connected with the present south abutment of the railway bridge. In 1919 the river bed had been silted Up to such an extent that the low-water level was considerably higher than the low-water level in 1878. and yet during the flood of 1919 the flood level was lower than tho flood of 1878 by 12ft 6in at Alexandra, (ft at Beaumont, 4ft 6in at Clydevale, and 4ft at Pukeawa. At these places the conditions other than that due to the Biltingrup of the river bed are very similar to what tljoy were in 1878. Tho effect of confining the flood waters between lovees must necessarily bo to raiso tho flood level; this point cannot be too strongly emphasised. In the ca&e of the big flood of 1878 no levees worth mentioning existed at Balclutha, and tho flood waters had a clean sweep across the peninsula. This resulted in a much decreased flood height compared with what would now be the case should a flood of similar dimensions occur, when the flood waters would be confined by the levees to a de. finite channel. 1 The commissioners estimate that a similar flood to that of 1878 would, under existing conditions, be between sft and 6ft higher now at the traffic bridge than was the case in 1878. Therefore, although the corrjmraioners are recommending the construction of levees verv much higher than the height to which the 1878 flood rose, they are, nevertheless, only providing for the same amount of water as came down in that flood. On the Balclutha Peninsula, below the traffic bridge, there are. three methods which may be adopted: EXTENSION OF THE LEVEE. 1. If the Railway Department desires that its line should be above the new flood level, and is prepared to pay for raising the line, including the station yard, then the railway should lie raised, in which case the railway embankment wiuld form tho levee from the south end of the railway bridge to the high country below the Balclutha Railway Station. Z. If, on the other hand, the Railway Department considers that it is preferable to take the risk and suffer damage when extremo floods occur, the balance of the town should be protected by raising the present levee which surrounds tho show grounds, continuing the same down Glasgow street, then parallel to the railway Itna into Baxter street, and thence by i-Tcewart street beyond the junction of these two streets to connect with the high country at Rosebank. Where the levee line is in a street the street should bo raised, and act as a levee 3. The existing railway bank might be used down to the vicinity of the present flood opening viaduct, this viaduct to be removed and replaced by an embankment above flood level down to Glasgow street. Tho levee could then be taken round tho outside of the station yard to below the goods shed. A gap could he left where it meets the two sidings serving the goods shed, and protection could be afforded by raising the _ goods approach road to the necessary height, and from the present level ciossinj to tho hill, by building a small bank as an adjunct io the present formation on tho river side thereof above flood level. The gan in tho levee where the goods shed sidings would pass could be olosed in time of flood by means of stoplogs dropped into a groove prepared in concrete abutments. The commissioners recommend the third method. Irrespective of which of these three schemes is adopted, it must be clearly understood that the levee must bo carried down the river bank,below the traffic bridge and connected with the railway bridge abutment. RIVER DIVERSION. (d) The bend of the river about two miles below Stirling known as Pillans's Bend should be cut off by a river diversion, and also the bend of the river known as the Ba.lloon Loop, near Kaitangata, should be cut off by a diversion. In neither ease is the diversion shown along the shortest route which could bo found, but they are so located as to give easy curves, swinging off the existing alignment in such a way as to minimise the chance of future erosion. The result of these cuts will be that the average slopo to the sea will be considerably increased, and they will thus minimise the tendency of the levees to raise the flood level when they control the flood waters within tho actual boundaries of the river. STIRLING AND INCHCLUTHA. , (e) The present Hermitage levee should I be .raised and continued down stream as far as may be necessary to the grade and levels shown. At the first diversion referred to above tho levee should continue round the existing channel, and at the Balclutha Loop the levee should follow the Swamp road to tho Kaitangata traffic bridge, and from thence run to the tidal gate recently constructed across the Tuakitoto Canal. From that point onwards it should run into the hillside at Kaitangata township. From this point onwards, the areas of land being small and the flood being never likely to rise far above tho existing banks, a very small levee will _be sufficient (f) At all points on Inchclutha where tho natural banks or the existing levees l'all below the proposed new grade the levees should be raised to the levels shown, 6ft wide on top, and with side slopes of 2 to It These and all other levees should be ' constructed of tho best material obtainable in their immediate vicinity, and should bo constructed in such a way as to give the maximum of consolidation. The levee following the right bank of tho Matau branch will, of course, follow tho proposed new cuts. In this locality it may be desirable to raise the road to act as a levee. On tho left bank of the Koau branch, where tho existing levees are so close to tho river as to be threatened by the erosion of the banks, they should bo removed to a safe distance before being raised in a similar way to the grades and levels shown. (g) The existing levee which now connects the high land in the vicinity of Mr Telford's residence with the railway bank at the Waitepeka Canal should be raised to tho level shown, joining tho railway on its jiew grade. From this point onwards a levee must be carried down towards the sea under tho same conditions as the othors —that is. to the levels given, in the approximate location shown. (h) Tho Catlins branch railway, where it passes over the Waitepeka Canal, must bo raised so as to be safe from inundation by a flood at the probable new heights. (j) All drains now discharging into the river at such levels as would provide a channej for invasion of the adjacent lands by the floods must bo provided with flood gates.

(k) Tho levees at present protecting Barnogo should bo raised and mado continuous to tho grades and lovels shown. All tho lovels given ure in terms of tho Tuape.ka railway survey datum. With tho height of tho Iravees givon on tho plana, it will bo seen that the road bridge over the Matau branch at Stirling is not sufficiently high, Tho commission has not recommended raising it in view of tlw fact that it is now a very okl bridge, and because, in the opinion ol tho commissi oners, tho community will bo justified in aooopting tho risk of its destruction until such timo as it requires rebuilding. When rebuilt it must bo constructed at a liigh enough level to ;iilow reasonable clearance above tho probable maximum Hood slope. If carried away before it is rebuilt, it will not jeopardise tho other bridge further down, as, owing to tho cut at the Balloon Loop, the main current of the river, if not the whole of it, will be diverted from that bridge. The commissioners consider tliat all tho land lying botween parallel stop-banks, or between any stop-bank and the edgo of the rivor, should be acquired by tho controlling authority. This will obviate claims for compensation by the owners of farms in tho bends which arra to be cut oil', while tho controlling authority will be ablo to lease the lands when the works are constructed, probaby at very littlo lees than the interest on the cost of their acquisition. Before any work is put ill hand the controlling authority must make a complete survey to enable the levess to bo constructed on the best linos in such a way as to minimise tho cost and reduce the flood levels as much as possible. THE RABBIT MENACE. Provision must be made to exclude rabbits from the levees around Balolutha, and eternal vigilance must be exercised throughout tb? district to prevent any of the levees becoming a harbour for rabbits. Otherwise a senss of false security will be engendered. DRAINAGE WORKS. 4. To ascertain the nature and extent of any drainage works that may be required, and the best method of carrying out such works. The river protection works recommended previously will not render the position as regarijs drainage any different from what it is at tho present time. Li other words, they will not render any more drainage works necessary. Consequently the Commissioners have not gone exhaustively into tho. question of drainage. At least three of tho subdivisions of tho district—Barnego, Otanomomo, and the Lakes district—require improvement of drainage to a greater or less extent, and tho same can apparently be provided without great difficulty. At Barnego one main drain is required, approximately as indicated, running through the lowest ground, but the levels of the land are so even that this drain oan I<e varied in position to suit the subdivision or internal fences. At Otanomomo tho old channel of the Waitepeka should be opened up, and a system of branch drains connected thereto. Here, again, the levels of the ground are such that the positions of the drains will be governed more by the farming operations and subdivisions than by any natural features. ' The draining of the lakes district is a very complex problem. Possibly something on the lines of a contour channel on the soaward side of the lakes, picking up Lovell's Flat, and carrying off the drainage from something over 50 square miles, would deal with_ the greater part of tho water. Owing to the position of tho Taratu Coal Company's railway line it would be advisable to place this line on top of the levee, which would constitute the lako side of tho contour channel, or to divert the railway so as to connect with the New Zealand Coal and Oil Company's private line at or near Kaitangata The body carrying out the 'necessarv drainage works should be a drainage board elected from that portion of the river trict affected, and these drainage board areas should coincide with the river ridings. COST OF PROTECTION. 5. (a) To furnish estimates of the coat of such remedial measures as you may recommend 6hould be.taken for tho effective control and improvement of the said rivers and their banks. The coramisioners estimate the cost of the remedial measures recommended by them under Reference No. 3 at £165,000. This c-stimate is based on earthwork at is 6d per cubio yard. . 5. (b) To report in the case of each r iver what area or areas of land should be constituted a district in respect of which a rate *may be levied to secure and pay the interest on and provide a fund for the repayment of any loan that may be raised to carry out any river improvement works which you may recommend should be undertaken. RATING AREAS. The areas recommended to be constituted a district in respect of which a rate may be levied to secure and pay the interest on and provide a fund for the repayment of any loan that may be raised to carry out the river improvement works recommended by the oommisiosners are as follows:—The portion of Barnego Settlement, the whole of Balclutha Borough, the whole of Incholutha, the whole of the Lakes District, the whole of Otanomomo district, and the whole of Kaitangata Borough. Each of the above districts should contribute in the following proportion to the capital expenditure required to build the whole of the works:—Barnego .03. Balclutha Borough .14, Inchclutha .20, Lakes District (Tuakitoto and Kaitangata) .10, Otanomomo district .09, Kaitangata Borough .04— .60. These proportions are based on the economic value of the protection to each district. ' The cost of maintenance shall be borne by the following interests in the respective proportions set out hereunder—namely: Barnogo 4 per cent.. Balclutha Borough 22 per cent., Inchclutha 31 per cent., Lakes District (Tuakitoto and Kaitangata) 16 per cent., Otanomomo district 15 per cent., Kaitangata Borough 6 per cent., Coalmines 6 per cent. The general Government shall not contribute to tho maintenance of the works. The commissioners reoommend that the rating should be an the capital value of all rateable property within the areas specified. As in each of the areas specified some portions receive more benefit from flood protection works than others, and other portions may receive no direct benefit at all, it is recommended that the rating be graduated, ae defined in tho River Boards Act, such areas as reoeive no benefit to pay no rates. The fixing of the rates in each area should be tho duty of the controlling body hereafter described. The commissioners recommend that the balance over and above the 60 per cent, as above be contributed a& follows:—Coalmines .04, Railway Department .03, General Government .33 —.40. . , . SPECIAL LEGISLATION RECOMMENDED. 5. (c) To report your opinion as to what matters, if any, should 'be adjusted by legislation. The commissioners consider that the whole of their findings, as set forth in this report, should be enacted in speoial legislation, to bo called the Clutha River Improvement Act. ONE CONTROLLING AUTHORITY. 5. (d) Generally to report your opinion on all matters arising out of or touching the premises, including the question as to whether or not one or more competent authorities shall be appointed to control the whole or any portion of the said river, and what statutory powers should be possessed by such authority. The commissioners consider that for the purpose of carrying out the works described generally in their recommendations under rc-ferenco No. 3, and ensuring their proper maintenance in the future, also for the proper control of the river and for the better protection of the interests of the whole community, one controlling' authority should be appointed. Tho district to bo controlled, and over which rates shall be struck to raise portion of the moneys required for the protection works, shall comprise the whole of tho six areas referred to under reference S (b), and this district shall be termed the Lower Clutha River Trust District. Each of the areas comprising the district' shall bo termed a river riding. Tho trust shall be composed of six local representatives, one member being elected from eaoli riding, and also of two Government representatives called River Commissioners, appointed for throe years by the Minister of Public Works, ono of the Government representatives being preferably a stipendiary magistrate or some person fully qualified and experienced in local body work, and the other an engineer with expr»'t knowledge ol river control. Your commissioners further recommend that the duties of this controlling authority bo clearly set out as follows: — (1) To have detail surveys, plans, estimates, and specifications made for carrying out the works recommended nlxrve. Theso plane shall be approved by the Government nominees on tho trust. (2) To assess tho total sum to be derived from oach riding in tho proportion recommended, and to fix the rates on all propertics in ench river riding, in the ratios of tho benefits to be derived, according to the principles laid down in thra River Boards Act.

(3)To sulim.it tho proposals to the ratepayers, and obtain their authority by poll to raise tho neoeasary loan. (4) To aarry out tho necessary work, eithor by contract or direct labour, in as expeditious a manner as possible. (5) To maintain the works efficiently, and to do whatever extra work may be necessary to improve the regimen of the river, and sooirro tto? fullest protection for their district from floods. (6) To take all necessa-ry obeetrvutions, and keep records tliat will assist in the study of tho hydrology of the river, changes in its regimen, hoights and duration of floods, ieto. The trust should have all tho powere of a local body, and, further, ahould have absolute jurisdiction over the channel and banks of the river, inasmuch as proposals for all drains emptying into the river, all locks, tide-gates, bridges, ferries, wharves, etc., ."hall bo submitted to and approved bv the trust before being carried out. No planting or cutting of willows shall be done except by tho trust. DRAINAGE. Eaeh of tho ridings mentioned may be formed into a Drainage Board to do the drainage work of its riding, and may obtain repprts, plans, and estimates of drainage works required from the River Trust. Ihe drainage board shall then proceed to raise the money from its area, and having done so shall carry out tho work itself, or request the River Trust to do so. Tho maintenance of tho drainage works shall be done by the drainage board. GOVERNMENT NOMINEES. The River Commissioners may be appointed as Government representatives on any river trust similarly constituted, and they shall report progress to tlio Minister of Public Works after each meeting of tho river trust. It shall also be their dutv to see that all valuable data; is collected and forwarded to Wellington for embodying ia the Government archives. INSURANCE FUND. The Commissioners consider that the following sums should be paid by the various interests in tho proportions set out below, towards an insurance fund, tho sums to be set aside annually and invested in a similar way to that in which sinking funds are controlled, as an insurance fund from which shall be met the cost of repairing or paying for any damage, not including damage to river protection works, which may occur by reason of tho possible failure of the works: Barnego, £20; Balclutha Borough, £100; Inchclutha, £160; Lakes District (Tuakitoto and Kaitangata), £80; Otanomomo district, £70; Kaitangiita Borough, £30; coal mines, £30; general Government, £110; —£600. It is recognised that any work of man, however well maintained, cannot be considered as absolutely infallible. While your commissioners consider that their recommendatioas will enable any flood such as has been experienced hitherto to be safely passed, nevertheless failure might occur by reason of faulty maintenance, a flood of unprecedented magnitude, sudden erosion due to a oh an go of direction of current during a flood or other cause. _ Should such failure occur certain of those intended to be protected will suffer much greater damago than others, and it is to recompense them for this, and to make the sacrifice equitable, that the insurance fund is recommended. It has nothing to do w'ith expenditure incurred for the restoration of river-protection works which may bo damaged. Tile moneys for this insurance fund shall bo oollected by the Lower Clutha River Trust, and shall be invested as before mentioned. On the receipt of claims for damages the trust shall have an investigation mado by a stipendiary magistrate, assisted bv two ass'-ssors to be selected by the stipendiarv magistrate, preferably one a civil engineer and the other a farmer. The stipendiary magistrate shall call such evidence and take such steps as he considers necessary, and advise the trust as to the amount to be paid out in respect of each claim, and the' trust shall make the disbursements accordingly. In the event of damage being done greater than the amount of money in the fund, then the claims shall be paid pro rata from the amount available in the fund, and such payments shall extinguish all liability then existing. In other words, no claims shall be carried forward as a charge against other moneys to bo accumulated.