RIVERS COMMISSION.

Hauraki Plains Gazette, Volume XXXII, Issue 4302, 10 August 1921, Page 1

RIVERS COMMISSION.

The Waihou and Ohinemuri Rivers Commission, consisting of Messrs H J. H. Blow (chairman), W. S. Shortt, and G. Buchanan, resumed its sittings in the Paeroa Courthouse MONDAY’S EVIDENCE. In examination by Mr Porritt Mr William F. Mac Williams said that the 1910 flood was abnormal. Up to 1910 a lot' of mullock and debris was put into the. river. When the companies were dry crushing they used . an enormous amount of firewobd. The hills round Waihi were covered with bush then, but the bush was cleared for firewood The removal' of the timber did not. he thought cause water to come down more rapidly. He could see no difference. Floods removed timber that had fallen Into the streams, washing it away. Floods nowadays were not more frequent than in the early days. The islands were completely gon?The Waihou' River bed was always moving, even at the present day. The Waihou was snagged right up to Matamata, in the liate J. C. Firth’s interests. Vessels going up to Matamata were shallow draught launches, but steamers plying.from Auckland to Paeroa could not go higher upstream. To Mr Clendon : He resided at Mackaytown for 14 years from 1875. The Ohinemuri’s velocity was greater than the Waihou’s, but from Cox’s downstream the river was practically “dead.” As a prospector he studied the floods. Part of the Watawheta had risen on one occasion 30 feet. He z saw 'the 1910 flood at its highest. Floods may have averaged six or eight each year for the 14 years he ' resided at Mackaytown. To Mr Gilchrist: There .were no bridges over the Waihou in 1880 near Te Aroha. He had done seme snagging in the Waihou. He vas droving cattle from the Waikato to Thamis for two years., A rise of 2ft 6in would effect the safety of cattlie being taken over Smallman't crossing. To Mr Johnstone : There was once a lot of al'kjsorts of timber on the Waitawheta. To Mr Buchanan : The islands ti; the Ohinemuri'were at several points between Karangahake and Marsh’s. When travelling up by boat in ut qarhy days to .the Puke the snags could be seen, as the water was clear. A 20ft. pulling boat could go up .o

Cox’s when- the tide was coming in. He believed Smallman’s crossing was just about where the Mangaiti bridge now stands. The brinks were steep. If the H river was in flood no attempt would be made .to take cattlie over. He had not been down either river by boat for many years,. He first noticed the Ohinemuri River becoming discoloured when mining tailings were deposited therein. Waite; J. Brown, retired carpenter, Waihi, said he, arrived at Thames i’i 1868, and went to Waitekauri about 1876. He was not familiar with the Waihou above Paeroa in the early days. He remembered the boats Boneventure, Pearl, and P,uby plying on the river about 1876 and afterwards. The Ruby was much smaller than the Taniwha and WaimarieBoats were frequently stuck in the river in .the early days. He had read of people being rescued from homes in boats. Sportsmen out shooting had told him they were able to make short-cuts between the Waihou and Piako streams during floods. He had been a Waihi borough councillor for 18 years. There were 21 or 22 bridges in Waihi. He recently inspected most of .the bridges, and some were showing signs of deterioration. The culverts in Waihi were in “a pretty bad state,” and the council had not sufficient money to repair them. To Mr Porritt: Witness had never seen the Waihou other than discoloured. The action of the steamers caused the discolouration. He had no experience of the Ohinemuri above Paeroa prior to residing at Waihi, and had never seen the “Ohinemuri clean, with gravelly bottom and grass growing to the water’s -edge. He believed the river depth was' the same to-day as forty years ago, but could not state the depth. To Mr Montague : Ohinemuri County contributes towards tb.e cost of six bridges under the control of the Waihi Borough. He did not know the present population of Waihi Plains. To Mr Clendon : Witness had resided in Waihi about 29 years. If most of the inward goods for Waihi came by boat to Paeroa for transhipment the navigability of the river would be of vital importance to Waihi. To Mr Buchanan : Witness was confident that he remembered the steamer Ruby plying on the river in 1876. John G. S. Ragg, master mariner, had engaged in river work on the Waikato for over 30 years. The vessel was a steam stern-wheeler, capable of carrying 100 tons dead-weigh 1 ;. The Waikato had become much worse in recent years, owing to shoaling, caused partly by draining and busn-

felling. The Waik’Sto rises more I

rapidly now than in former years. His boat travelled upstream 110 miles to Cambridge and Pirpngia. The first 90 miles was through pumice ana sandy country. Large drainage operations were being carried cut- on bo.tn sides of the river. Between Mercer and Tuakau the low-water level was not as low now as in former limes.. There was much more shoaling lower downstream. Draining caused shoal barriers at various points, impeding navigation. Between Mercer and Ngaruawahia there was a mass of shoals now. Boats had to cross 29 times in a length of 27 miles. Formerly there were not so many crossings necessary. To do any good several suction dredges would be necessary. Another course would be to construct training walls. To Mr Porritt: He had no knowledge of the Waihou. There was nobar at the mouth of the Waikato, and the channel at the heads was the same as c had existed for 60 years. The surge of the Pacific Ocean caused a rough entrance to the river. The River Board’s groynes did good at the imniediate locality, but away from the groynes damage was caused. Above Cambridge pumice came into the river. - No extensive snagging had been done on the Waikato. The Waihou was only a ditch compared to the Waikato. The latter stream was adversely. affected by moving sands. The Waikato sand gradually works out to sea. The last 35 miles of the Waikato had a fall of six, inches per mire. To Mr Hanna : Waikato sand binds with mud, where the river is “dead/” Irpnsand is particularly binding. A fresh may alter- a ,tightly-bound part of the river into a navigable channel. To Mr Gilchrist: The barriers are moving and “aliive,” and each flora shifts them away. The varying degrees of fineness of sand would not make any appreciable difference in the deposits. The Waikato had not been artificially straightened'. To Mr Clendon : The average widtn of the Waikat. below Hunt’ly was about 22 chains. The whole river between Mercer and Huntly was shallow. The bed there was of fine glassy sand, with small patches of shingle or mud. No mining, debris was deposited in the Waikato., . To the Commissioners ; Sandbanks of forty or fifty acres frequently shift. The width of the river contributed to the formation of sandbanks. The river velocity is not increased during'floods, as the extra water spreads out over neighbouring land. The Waikato is gradually narrowing owing to the planting of willows, which

arrest the shifting sand. Harman R. Young, C.E., Cambridge, and formerly Public Works engineer at Paeroa, said at present he was engineer to . the Fencpurt Drainage Board and Macgawhara River Board. He presented an enlarged plan of the Waihou River, which was prepared to show the overflows of the Waiho.i before the present improvement works commenced. The first overflow downstream from Te Aroha is about CJ chains below Mangsriti. A furth-;,’ plan was .presented showing the area?, and boundaries of the districts coatrolled by tire several local bodies in the Thames Valley. In 1911 he was appointed local) engineer in charge of ;<.he Waihou and Ohinemuri Rivers improvement .works. Up to that time practically no data was available. Some work had been done prior to that time in the vicinity of Waitakaruru, and a start had been made on .the lower portion of tae Waihou. He collected data io show' the maximum flood discharge, upon -which to base his scheme of operations. 'He maue cross-sections at Mangaiti \( Waihou) and Mackaytown (Duinemuri). The flood of 1910 was considered the record flood in the knowledge of settlers. He prepared plans of the proposed “cut” at Ngara’ahi and Rputu. At Mackaytown there was plenty m silt on .the river banks, but at all points except opposite Marsh’s the pastures had recovered themselves. According to the depth of silt deposit on thbse sections he classified the land. This was. about fifteen months after the flood of 1910. He follow.-d the requirements of the Act in classifying. Land with sil;t of 3in or more was classed as destroyed land, and parts where the deposit varied from %in to 3in the land was classed as partly damaged. Most of the damaged, land had recovered when inspected 18 months later. Barrett’s properly had some silt on it. Tetley’s was different, for a few acres of this had nc recovered. The basis or compensation was fixed by the Act. A Compensation Court awarded compensation, which was duly paid. On later inspections he found only a limited aria that had deteriorated as i result o. the flood,. He was not speaking as a practical farmer, but apparently the greater part of the lapd was as goed as lands adjacent that had not been flpoded. From May, 1911, io September, 1918, he was in charge A, Paeroa, and could recollect nc complaints of flood damage, neither to land noe stock thereon? He knew of no cattle being injuriously affected by the

mining deposits in the water. A contract was prepared tor surface cut.> at iNgarura.m and Koiv.u, ;<ne tuts to be 3tt deep and i6bit •vine, I lie cpeii tnerefrom was used to ioim verbanks. The spoil comprise - : clay and sand, similar to nearly all .tne Hauraiii Plains land, m 1913 a hydraulic dredge was used to dnTie Hie i nannei, the spoil being u.=ed to stungilie.n the stop—banks. The cut gave an increased fall pf nearly -1 it at 10-. v tide, and reduced the leiigt.i ol the river by three miles. Hie Ngaiaram and Routu cuts were one m.le in length. The willo.w work j’ist above the Ngararahi was commenced, about tne end of 1911, Ultimately the whole of the Waihou banks fro n Ngararahi to Te Arolia were clea.x-1 of willows. Part of the Ohinemuri was similaily* treated. From Te Arona - downstream the effect of the willows was to decrease the velocity of water and to create banks in the stream. Jae removal of the willows cau.ei’. the. more recently formed banks to move downstream. Before the wi lows were iemoved the fairway would be only about 15ft', The river has been maue much more efficient for t:it draining of the surrounding couT.ty. Tne removal of willows has had a very beneficial effect upon the whole oi the country, including Te Aroha. The ißiver has probably not been appreciably deepened, but the velocity of the .water has been increased. The flood slope pf the river was not gieatly affected above Tirohia. There were no differences ip the level at Mangaiti, Most of the shoaling was between Tirohia and Te Aroha. He knew of complaints or shoaling cn that section, but. considered .the Ngararahi cut had not affects J the depth of the river above Tiroh .a, The land above Tirohia had been imvijiea as a result pf the willow removal alpng the river. In November, 1914, as a result of urgent representations that flooding of Netherton lands should ne relieved, he instituted records, Al Netherton there was a sh.eet of water about Ift deep. He expedited stopbanking at the point of overflow to prevent a recurrence. He helieved tha.t stop-banking had been completed. Netherton was now free from any Jbu.t extraordinary floods, which might arise from the Fiako and Awaiti overflowing. Stop-banking Between Mangaiti and Tirohia won 1 '! make Netherton absolutely safe. He was confident the stop-banking had benefited land "in the neighbourhood. Some pf Nicholls’ land had been bought for £7 per acre:when it was liable to fio.ods. It had been sold for £l9 within the liast five years, and was now worth.about £35 per acre. Other properties • showed an appreciable increase in selling values. The Awaiti Government settlement, wh«i it was subject to floods, was i valued at £lB per acre and sold at that figure. To-day it was worth £4O per acre. An extremely high food in the Waihou—the equal of the 1907 flood—would cause the flooding of a grpat portion of the Awaiti. During jjis residence at Paeroa about six floods had broken across the Awaiti from between Mangaiti and Tirohia. When the stop-bank on the. west side of the Awaiti ridge is constructed it will assist to reclaim a huge acreage of land at ;t'he back of the ridge. All this work was in the 1910 Commission’s estimate pf £150,000i

Mr Clendon pointed out here that the £150,000 was purely a guess. Continuing, Mr Young said the delay in stop-banking above Tirohia was necessary until! there is provision lower downstream for coping with the water that would be brought down. The dredgings consisted chiefly of pumjee sand and quartzite obviously brought down from up country. At low places he could see continually shifting streams of sand. The dark particles of sand resembled ryo'litic rock fragments, which were of volcanic origin. The first work done was in 1916, when a stop-bank was formed from Thorp’s Pill to the Junction. This was the obi course of. the Waihou. but is now known as the lower Ohinemuri. The dredgings from this area were chiefly pumice sand, with about 10 per cent, of mining’siltMining sil.t was not suitable for making stop-banks. About 50.000 cubic yards of material was dredged in this section. Ultimately a complete stopbank was made from Thorp’s Bend right up above Paeroa. This wai principally to protect Paeroa tow ’. The Ngararahi cut contributed considerably to protecting Paeroa from the floodwaters of the Waihou. Ail local bodies turning water into th? Vivers should contribute towards the cost of the rivers ' improvement scheme.

To the chairman: Paeroa should contribute if the whole scheme is to be carried out. Mr Clendon : Waihi also. Witness proceeded to detail the work done to relieve 2000. acres of swampy land at Rotokohu. This area was “a kind of basin,” caused by a ridge near the river bank. The bulk of the water that keeps that land wet comes from, the Waihou. Some comes from the Rotokohu stream. Early in 1917 he received instructions to improve the Rotokohu area, and he put gangs on to cut the top of the drain. The drain had since been excavate 1 to its full depth by dredgingi The Rotokohu swamp had always been there; it was a raupo swamp. There was not yet a stop-bank on the left bank of the Ohinemuri to protect the Swamp. Two floods from the Ohinemuri had' crossed Rotokohu to the Waihou during his knowledge.. Stopbanks had since been constructed oji both sides of the Waihou below Pacroa. Wuarves and sheds pt Ngahina were completed in February, 1919. In his opinion portion of the'Ngararahi, •and portion of the. stop-bank from the butter factory to Thorp’s Hill, were necessary by the discharge jf mining tailings into the Ohinemuri. When the stop.bank of five miles between Tirohia and Mangabi is completed 38,000 acres of swamp land—of which’ 31,000 acres is- Crown land —will be reclaimed. As the improvement works progressed the Native lands (part/of jthe 7000 acres) were gradually sold to Europeans, who

resold as the works furtftcr progressed. Three-fourths of the 38.000 acres was peat land—that Is, land covered with peat from 3ft to 40ft in depth. A iot of that land had deposits of pumice sand and vegetation. When the stop-bank is finished, if a canal of six miles m length and 12f< in width is made right through it th? whole of the land would sell at a very. ’ satisfactory figure. The whom of the Hauraki Plains had a peat deposit of from 3ft to 40ft. The peat will shrink, but still permit of sufficient fall for adequate drainage. Th? land behind Tirohia would not be a.j good as Netherton "land. Tahuna- land had not such depth of peat as on this side of the swamp, but Tahuna-iPate-. tonga peat - land Had been sold at from £45 to £6O per acre. Between 40,000 and 50,090 acres of Hauraki Plains land had been sold under the Hauraki Plains Act-. He be:ieved this would average about £7 per aci->. With Messrs Adams and Banks he took a series of test samples from the beds of the Waihou and the Ohinemuri. He had not noticed any appreciable pinching of the .banks of the Waihou as a result of the mining silt being deposited in the Ohinemuri. The Gold Extraction Co. cleared, out a large quantity of mining tailings, sand, and snags, at points upstream from the works. Slimes from the reduction operations were shot into -the river agate. At this stage argument ensued as to the admissibility of evidence as to cross-section figures prepared, and the witness made it clear that the figures he had quoted were obtained by the Public Works Department.. On resuming, witness said th i lands immediately benefited by the Rivers improvement works included the Te Awaiti-Government settlement of 2000 acres. Approximately 500<) acres- were benefited by the Ngaiarahi'eut and .the stop-banking up to Tirohia. In addition about 2000 acres of Roffikohu swamp had,, received direct benefit. At flood time and hign tide, from Mackaytpwn tp the Ngahina, the'central surface velocity was 6ft per second. At normal times the velocity was about Ift per second at high tide. From Mackay.town to the - junctiph there was a fall of 34.3 ft. The distance was six miles, approximately. The land southward from the Firth of Thames in pre-settlement times was affected by the flooding of the Waihou. The Waihou could only carry one-third of the volume of water that came down; therefore -he other two-.thirds had had .to spread acr.oss country to the ftakol Bores put down showed a depth of 120 ft of vegetable matter. He believed about 4,000,000 tons of solid matter -ivere still being brought down the. Waihou every year. The bed of the , lower Waihou is no worse now than in 1910 for navigation. The process of _ na " tural reclamation was still going on, just the ■same as for ages past, when the Waikato had its outlet to the Thames Gulf.' At. present the fall per mile r rom Ngahina to the sea at low water is only 3in, The flood discharge in the 1907 flood was 28,000 ft of the Ohinemuri and 12,000 ft of the Waihou. The strong stop-banking now in progress was designed to keep the water within its banks. Only about a mile of the Ohinemuri from Paeroa to '.the junction remains undredged. If the Pereneki cut is put in the dredging will not be necessary, for that portion pf the river will become a lagoon or backwater. Sand from the river banks near Wharepoa is removed in barges for building purposes in Auckland. The sand would have to be fairly, clean, hard sand, practically free of mining debris, if it was to be used successfully for building operations. Mining tailings travel in suspension ?n the water until they reach -the tidal area, and in flood time a large pitportion is forced down into the Wa.hou below the junction. Very little remains more than a ■short time i i the Ohinemuri, To Mr Porritt: About 6ft of the 34ft fall from Mackaytown tp Ngahina was in the first mile. The next mile has a fall of Bft. The third mile, (down to the Criterion bridge) had a fall of 6.7 ft The- next mile omy - showed a fall of 2%ft, and the fift.i mile a little over Bft. The flood i<i the ' Ohinemuri in September. 1912, reached within Ift 9in of the previous highest level. He had had no official complaints of cattle suffering from the floodwater, which contained mining silt, and caused cattle to lose their hoofs and hair. He understood the main outlet drain from the Awaiti Settlement kept itself clean. There . had' been numerous complaints from settlers of damage caused by flooding, who wanted more expedVion made with the improvement works. He made a thorough survey of the-lan.l between the Waihou and Awaiti streams. One object of the stopbanking was to confine the river, which, by its greater velocity, would drive mining debris and other material out to sea. The Rotokohu drain had been made by ,the e Department to rectify damage done by the Ohinemuri overflowing on tp the swamp. He was not aware that Hie settlers vFere contributing towards the cost. .The Extraction Co.’s operations were beneficial to the river. The company had been seriously hampered by the deposits of silt coming down from higher upstream.

TUESDAY’S EVIDENCE.

QUESTION OF COMPENSATION. Resuming on Tuesday, the cross- •

examination of Mr Young continued. Replying to Mr Hanna’s question as

to ,what the effect would be ifi stopbank’s were put on the left bank only, witness said the land would-be sub-, iject to flooding, that is, the area above Mackaytown.> He considered it; would be cheaper to buy the land than to ereqt stop-banks. / Mr Hanna gave some of the prices’ paid by way of compensation: Soren sen, £l6 Ils 9d; R. Foyey, £6; Marsh and Brown, £B6 6s 9d. He asked wit-, ness if He thought this compensatin'! was sufficient, in view the fact, that the 1910 Commission recomgiend* ed the erection of a stop-bank, 'Whica -■ was. not put there. Witness said that, under cumstahc.es the question of compel' • satipn might be reviewed, . *

Witness admitted that the floodgate below Cassrels’ drain had given way. This gate had been repaired, but although flood water had gone through he .did not think silt had. The distance from Mackaytpwn to Ngahina was five miles.. He denied Mr Hanna’s assumption that there was two hours’ duration of dead wa,ter bet,ween the rise l and fall f the tide. The inflowing current came • as far as the Paeroa bridge. There would be a fall of 14 feet at ordinary tide. Mr Hanna: What velocity would that give ? Witness : That would need a very intricate calculation. You may get it from-the Public Works Department. (Laughter.) EFFECT OF EDDIES. The Extraction Co. dredged out to a depth of ten feet, but this pocket would All up with heavy or coaise sand, and not with fine silt, as the latter would be washed out. At any place where eddies occurred theie was bound to be silting and a deposit would be thrown up on the bank. If there was a stream the size of the Mississippi it would not wash the silt away from an eddy. Commissioner Blow: As a matter of fact the Mississippi shoals rather badly. Mr Hanna asked if the mining tailings dredged out when stop-banks were being made would not run back into the river. ) Witness : Two per cent,'the other eight of .the total of ten per cent, of tailings in the excavated matter remaining on the banks. LAND DECLAMATION. Witness said that without the river works the lands they protected would not have been workable. Land had gone up in value in the Waikato, but he had never heard.of any such sensational rises as had taken place on the Hauraki Plains. Waihou West »No. 3 lands were bought for £7 per acre (£B, corrected Mr Hanna). The owner had refused £l9 an acre. Mr Hanna: Would you deny that Mr Carter bought it for £8 per acre ten years ago, and. sold it to Campbell for £l2 an acre —No, but Western, the present owner, refused £l9Regarding Rotokoliu swamp, witness admitted that this had been ploughed at one time. To Mr Gilchrist, junr.: The Ngararahi cut lowered the Waihou as far up as Tirohia. Unquestionably it lowered the level at low tide, but did not affect it above Tirohia.. He, was certain the river had not been lowered by the cut by two feet up to Te Aroha; Had such a thing occurred certain lands now immersed' would be ■ drainable, whidli they were pot. The cuts would not improve navigation, but the drainage was certainly improved. The two things did not, run together. The remedy, without question, was dredging. (Still sitting.)