CONTROL OF THE RIVERS

Hawke's Bay Tribune, Volume XVIII, Issue 47, 7 February 1928, Page 7

CONTROL OF THE RIVERS

Investigating Committee at Work

TAKING OF EVIDENCE CONTINUES

The Hastings Sitting

The hearing of evidence by the investigating committee of- engineers, Messrs. A. J. Baker, H. Vickerman and J, D. Holmes, into the problem of the control of the Hawke’s Bay rivers, was continued at Hastings yesterday afternoon. Mr. G. Rochfort, engineer and surveyor, reviewed the effect of several big floods, erosions, accretions and the alterations of river channels. Mr. A. Bainbridge explained the point of view of the settlers at Raupare, dealing especially with the question of seepage. Lengthy evidence was given hy Mr. J. A. Miller, chairman of the Hawke’s Bay Rivers Board, in connection with both the Tutaekuri and the Ngaruroro rivers, referring es- • pecially to the proposed diversions of both rivers. Continuing his evidence. Mr. Rochfort said that prior to 1867 the Ohiwhia stream existed on the line of the present Ngaruroro river. The Ngaruroro discharged below Roy’s Rill and around by Havelock North.,« The 1867 flood, being a heavy one, went over into the Ohiwhia, and in five years time formed the Ohiwhia valley and had connected the river with its present course. This showed that it was not a sudden diversion. Mr. Rochfort said that he had never heard of a computation of the material eroded from above Fernhill, but he could make up an estimate. RAUPARE DRAINAGE. Mr. A. S. Bainbridge, chairman of the Raupare Drainage Board, said that his experience of the rivers was confined to the Ngaruroro. to which i his property abutted. During the past | five years near his property the shingle had been raised about four i feet, rising steadily after every fresh > in the river. This was viewed by the 1 Drainage Board as ultimately inter- ' fering with their drainage system I in that there will be a lack of fall. . Their only outlet to the river was I governed by a flood gate. The main 1 drain, which was taking the bulk i of the water, was greatly interfered | with by the last flood, it being choked up with rubbish and no compensation had yet been paid to the ratepayers bv the Rivers Board. Nir Miller: We hope to pay something. Mr. Bainbridge, continuing, reviewed the serious losses sustained by some of the farmers in the March and subsequent floods. He pointed out that with the danger of floods removed the value of properties in his area would be greatly enhanced. Seepage was another serious problem, said witness, in reply to the chairman’s remark that any future bank-building might be done systematically and to sufficient levels. Settlers could not see where banks were of use when they caused seepage through their being built above the level of lands adjoining them. In his opinion no system of flood control would entirely eliminate seepage. Referring to the banks, witness said that they did not breach in 1924 until after the waters had overflowed for some time. THE WHAKATU BRIDGE. Mr. G, Purvis, a member of the Rivers Board, referred to a motion that he brought before the board in 1924 to engage an engineer to prepare a scheme to provide the same capacity under the Pakowhai bridge as under the Fernhill bridge; also to ; report upon the lengthening of the Whakatu railway bridge by 200 feet. Mr. Purves put in considerable data concerning bridges and the dredging of the Tutaekuri river overflow. He had put a lot of time into the river nuestion, but unfortunately no finality had been reached. They had found the Government were up against the board in regard to the Whakatu bridge. They had since proposed to do a little but not a great deal. He was satisfied that with that bridge lengthened by 200 feet practically the whole of the trouble would be overcome. The Clive bridge was capable of taking twice the present amount of water. Regarding the Tutaekuri river and a new traffic bridge, he was confident that if it was sheaf-piled and carried well out it would be more satisfactory than concrete piers should there ever be any scouring. With the lengthening of the Whakatu railway bridge it would he necessary to widen the river bed down to the sea. He was afraid that the little assistance promised by the Government in connection with the bridge would not go very far in the solving of the problem The question of accepting a scheme would depend a lot on the confidence that the people have in the hoard. He agreed that it would he reasonable to cany out the whole scheme and not any one part of it. which would only affect one particular area of the district. He pointed out that there was a area in the lower end of Chesterhope which was a natural overflow through which the river always flowed. An overflow there would offer the least trouble of any to the settlers. SCHEMES OPPOSED. Rather than see Mr. Hay’s over- | flow scheme carried out, Mr. Purves | said that he would prefer to go oft the hoard. It was an engineering I feat and might be accepted if no j other scheme were obtainable. He I was strongly opposed to “The Pines” overflow as he considered that the i country was of a very unsatisfactory nature and that it would probably mean putting the Tutaekuri straight down over Tarada 10. The bank at Otatara was taking it all its time to cope with the present floods. If the banks for the Tutaekuri overflow as proposed by Mr. Hay were put up il would mean that the water would he confined to the washout bridge, which had a lesser capacity than that of the Redeliffe bridge. He was strongly of the opinion that thorp should ho two outlets through the beacli—one at the Washout and one lor the Ngaruroro. Although a considerable amount of water went through the Waitangi bridge no scour was ever noticed,

which was no doubt due to the great angle that the water had to traverse, which naturally restricted its velocity. To the chairman, Mr. Purves said that lie realised the great necessity of carrying out a scheme to deal with both rivers and that unanimity was necessary on the board and in the district. Personally, lie thought that the greatest danger would come from the Tuki Tuki in years to come. To do the three rivers would cost about £250,000. The chairman: No such scheme is at present under consideration. | Mr. Purves, continuing, said that he felt that the district would be prepared to carry a loin for about £120,000 to deal with both the Tutaekuri and Ngaruroro rivers. Mr. Purves pointed out that years ago the Government were talking of moving various Government institutions from Napier to Hastings owing to flooding. Protection was carried out and now the people did not recognise these embankments as protective works and were of the opinion that they should not be rated. MR. HAY’S SCHEMES. Mr. J. A. Miller, chairman of the Rivers Board, in referring to the diversion of the Tutaekuri said that Mr, Hay brought down seven different schemes io r this undertaking, his “G’’ scheme being adopted bv the board because it would give greater relief to Taradale, would take the river further away from Meeanee and would not disturb the settlement of Pakowhai. This scheme was to cost about £90.000. It was felt that before the Ngururoro was dealt with it would be unwise to go to the I public for a loan. A modified scheme I for the Ngaruroro was accepted, upon i which about £15,000 had been spent. ; There were members on the board 1 who believed that another scheme would serve better and that the in- | take should be opposite Guppy’s road, Taradale. The bottom of the river there was 23ft., while at Taradale it was 18ft. The laud, through where it was proposed to take the overflow, had a datum level of 21ft. The present overflow for Mr. Hay’s scheme was feet higher than the land on either side. Meeanee would l>e adequately protected bv this course there being the new hank, the old bank and the high land in the present river-bed. In connection with the Washout entrance there were grave doubts that there would be sufficient water to keep it open, while the Ngaruroro always maintained its mouth. The question was really one of river mouths—the Waitangi versus the Washout. The Ngaruroro would have nothing t<j fear from the Tutaekuri and the bringing of the two rivers together would ensure a good mouth against any high seas. It had been suggested that the Waitangi did not release the water direct under the bridge. Mr. Climie’s idea was to cut off that bend and to enable the waters to flow more directly into the Waitangi and so obtain a better outfall. Mr. Miller raised the question of the mouth which had a tendency always to work north. This was illustrated by the concrete groin in the 1924 flood, when there wag a much greater space on the northern side of the concrete work. The position in the past has been a flood at the high tides. The effect of the tides was noticeable at Pakowhai. In 1924 when he saw it the water had no sooner reached its highest point than it started to go down again TUTAEKURI AND WAtTANGI. Resuming his evidence again in the evening, Mr. Miller pointed out that if the Tutaekuri were taken out through the Waitangi a considerable saving of £lO,OOO would be made to the board and consequently in the cost of the scheme. He maintained that whatever was done the water from the Washout would still go through the widened mouth of the Ngaruroro. Mr Hay had submitted a cost of £14,000 for a new bridge. The actua] cost to the board would be considerably less than that estimated by Mr. Hay, which would mean a further saving to the board of about £lO,OOO on the scheme. The Brooksfield bridge (GOft.i was damaged, be said, in the 1927 flood, when the approaches were washed away. It was realised that a larger bridge would be required, it not being provided for bv either Mr. Hay or Mr. Climie. A 400 ft. structure was considered to be necessary and the cost of it to be shared equally bv the Hawke’s Bay County Council and the Rivers Board. As finance permitted the bridge could be .lengthened. At the present time the traffic did not warrant an expensive bridge because it was not a highway and it only served a few settlers who would be convenienced during a flood. The diversion of the Tutaekuri and how it should be carried out was of great importance. It wa s felt that dredging the channels and builaing the bank by means of a dredge would be the most satisfactory. Mr. Hay had suggested a four-feet pilot channel, whereas various members would like to see a channel 10ft deep and 60ft. wide made. The chairman said that when providing a water-way the cheapest means was building up the banks. Dredging such a channel could not possibly compete with it. That method provided for letting the water do the work. Mr. Hay had allowed for (bat. THE BANKING METHOD. Mr. Miller, in reply to the chairman, said that he was rather surprised to hear that hanking would be, cheaper, liecause all the material used in banking cost about two shillings a yard whereas by dredging it would not cost more than about tenpence. The chairman stated that once the river was put through it would soon scour out a channel. Once the water was confined it would do the rest of the work. He then raised the question of securing a dredge, just to on a small job like that. Mr, Miller then mill a let ter received bv J lie board from a syndicate interested in re-

clamation offering to dredge the channel for the diversion of the river. Despite what engineers said, Mr. Miller stated that he was strongly in favour of deepening the beds of the rivers and decreasing the height of the bank. Referring to the Tutaekuri river at Puketapu, Mr. Miller stated that Mr. Hay had proposed to erect a bank north of the suspension bridge to give protection to Moteo. The board, however, did not erect it but planted a plantation for the purposes of trapping silt. It would have the effect of throwing the river on to a large area of level country. There was some high land upon which a small bank might be erected and serve the purpose equally as well as a big bank near the river. THE NGARURORO. “In dealing with the Ngaruroro,” said Mr. Miller, “one has to take into account the different floods and their effect. The question of record of highest flood may not be exceeded and it is possible that never again may such a flood occur. From this, I assume that flood waters to some extent will not come in such a volume in a short time, but the flood will last longer—take 1897-1924, over in a few hours while .the 1927 lasted a good two days. The 1919 report estimate the flood in this river at 180,000 cusecs. Mr. Hay provides for 136,000 (old channel 56,000, spillway 80,000) and suggests that a flood of this size might only occur once in 100 years. “I agree to a great extent-with this, and go further and say that I do not believe there has been a 70,000 cusec flood since '97. I have, of course, no data, but if Pakowhai bridge will only take 40,000 cusecs, any overflow I have seen over Pakowhai corner or water on Tomoana land, did not in any way compare with the amount going down the river. There was also breaks in Omahu banks in 1914. of which a great quantity joined the present course again below Pakowhai bridge per Tutaekuri-AVaimate. “But again in 1924 and 1927. the Whakatu bridge took all the water that got to that bridge (certainly some backing up on Tomoana and Whakatu lands) and this according to 1919 is a 60,000 cusec, though I believe Mr. Hay’s records show it as only 36.000 cusecs. The fact remains that engineers consider that in and over a period of years large floods occur a»d it is wisdom to provide for same up to about 150,000 cusecs. “It was hoped that the present bed could be mad© to take the bulk of such a flood, by clearing obstructions, straightening bends and more clearance under bridges, especially as the records show the river from Glazebrook’s bend to sea. canalized and deep could take perhaps double to treble, that now flows through Whakatu and Pakowhai bridges. It thus seems to follow to cope with a large or abnormal flood it is necessary for Ngaruroro io have an overflow channel and to decide the best place for this overflow “There seems to me and others (certainly laymen) that the further inland this overflow fs the better and that th e pressure should be eased near the seat of trouble, not afterwards. “You have seen the protection above Roy’s Hill to present overflowing there. You have also seen the immense width the river-bed at lower Roy’s Hill, and just above Fernhill—the great accumulation of water that can occur there. Now in 1897 this water not only got away below and by the bridge but also flowed over through Maori lands right over to Omaliii-Okuwa road (thence through Korokipo to Tutaekuri near Taradale, Tutaekui'i-M’ni-mate to Pakowhai and through lower Pakowhai). “During the last few years a very substntial bank has been made across Fernhill-Omahu road, up through Maori land to Omahu-Okawa road, preventing any get-away of the flooded waters by this outlet and confining the whale flood to the Fernhill bridge. The pressure then must be extremely great on the OmahuKorokipo and Twyford banks and to relieve this pressure the overflow should be as near as possible to this pressure. “The further the river travels and the banks become restricted as in Mr. Hay’s scheme, the greater the danger, such as at Raupare. This restriction is very great like forcing the waters into the neck of a bottle. “Mr Hay proposes the following capacities: 176,000 cusecs below Fernhill, reducing to 164.000. 152.000, 142,000 and 127.000 below The Pines. At present the capacities are: Below Fernhill 100.000. at Pakowhai 40,000, and at Whakatu 36,000. EVIDENCE OF PAST FLOODS. ‘ ‘lt seems evident from past floods the danger is from above Pakowhai bridge to Fernhill, any relief must be given there. There has been no trouble from the old Ngaruroro to th e sea, no pressure on any bank there, no flooding from river into Clive etc., yet Clive is only a few feet above sea level. Having also taken this fact into consideration in 1897, the present bed of Ngaruroro has risen at Pakowhai bridge 13 feet with a proportioned rise up to Fernhill, so that it takes a very small flood to fill the bed compared to 30 years ago. “The confining of this river by means of high banks when the present bed is so little if any below the surrounding country, is a very dangerous experiment, and if it is 'expected to scour the shingle and reduce the bed the point whether this river has yet formed its shingle alignment has to be taken into consideration, or otherwise the shingle may only disappear from one part to collect in another. “We are very much concerned re Mr. Hay’s scheme and view it with great fear. We fear the banking of the ponding basins at Tomoana, Chesterhope, and the discharge of flood waters over Pakowhai country, all of which have helped considerably to ease the pressure at Whakatu. and w e must also view with grave concern the floodgate and banking of Tjitae-kuri-Waimate as overflows at Moteo and breaks in banks at Omahu tho waters of which (a large proportion) flow into this stream and will cause a heavy pressure on. It seems to us most dangerous to erect such high banks, more especially in tho vicinity of Whakatu where on one side he is to have man-made banks at such it height as to force the water over a

solid land on the other side to the extent, of seven feet in depth. Taking also for such overflow land this is so valuable and practically only safe place in that district for stock in cas« of a serious flood. In heavy rain all the stock is gathered up from low lands and placed in this particular part. “The raising of the bridge 2ft. and lengthening it 250 ft. may have the effect of raising th e bed instead of lowering it. I do not think the lengthening is so important as the reconstruction, longer spans, giving less obstruction and being able to us© bed to full capacity and removal of stones, would canalize and probably give a greater scour than any lengthening. “There is also the question of main highway, Ar© w© to be permitted to run two banks across this road, and to leave an undefined open channel between? Is there not th© possibility of a channel scouring and requiring a bridge here. Personally I think if this scheme is considered, it would be better to have an overflow’ channel made, rather than have the high banks. “The flatter the gradient) the more likelihood of shingle depositing; therefore mor© shingle would accumulate at Whakatu overflow (also assisted bv the checked waters) than there would be at The Pines. ANOTHER PHASE. “There is another important phase. The banks at Twyford and Raupare were built long before northern banks. The floods, till northern banks were made, flowed over the country and built it up. This was materially assisted by tree planting. We have now banks built on land on the northern side higher than the southern side. In consequence manmade banks on this side must be higher banks. Surelv there is some danger in this. You have this closely settled valuable land near a large town, with the threatening menace of these banks and whose potential increase in value if the menace was removed (we believe can only be done with an overflow above Pakowhai bridge) would be quit© £2O per acre. Again, at Whakatu, on the northern side, the land is held in large blocks, whereas on th© southern side, you have very densely settled land in very small farms, fruit, dairying, vege tables etc., the village of Whakatu and the townships of Clive all in low country, and gravely menaced by the danger of a high-man built bank at Whakatu. There is also the menace of the important freezing works. The overflow of the Ngaruroro joining the Tutaekuri at the angle it does 1 consider grave danger would threaten the northern bank and also the lowlands towatds Napier, rhe Pines scheme may have faults, but it also has very great advantages, among them, as I have suggested an overflow where th© river starts to be restricted. It relieves the pressure on tho banks before, above and below and has a more direct course to sea, shorter, distance and a greater fall. It is a natural course, tlirougn the least valuable country (comparison of values Hay and Pines by F A. Cameron). It is carried through larger holdings, no close settlements, and for tile greater part when joined with die Tutaekuri saves area requiring one course, instead of two. It will be a big relief to Taradale. as the Moteo floods from Tutaekuri instead of going into Tutaekuri at Redcliffe will go down new course, away from Taradale, (It was no doubt these waters joined with Ngaruroro waters through breaks in Omahu banks that caused break in Taradale bank 1924). The dam at Maori pah, Redeliffe, will prevent any Ngaruroro, Moteo, Korokipo or breaks in banks above Fernhill, getting back into Tutaekuri. It will relieve the fears of the orchardists along Pakowhai to golf links road of any menace from above same causes, and from breaks in the banks of the Tutaekuri-Wai-mate. It will improve tho position of th© farmers at Pakowhai by removing the menace of banks breaking above them. All they then need fear is perhaps a backing of waters. This causes no losses. Again if. will relieve the Raupare-Twyford-Tomoana-Whakatu and Clive—closely settled districts. NEAREST POINT TO MEEANEE. “The nearest point to Meeanee will be three miles away and as they wish their river diverted to this course and taken out with the Ngaruroro mouth at Clive surely they cannot object to dive taking the surplus Ngaruroro waters down this course to be delivered again at the Ngaruroro mouth. They wil] navo further protection—a new bank still retaining two other bunks making three in all with all the high land between them. “The question of a new bed for the river may be in your minds, but don’t let a few acres of ground weigh in the balance with tilie lives of settlers. Believe me, this is likely, as high banks filled with silt are just as likely to break in the future as they have in the past and these high banks create perhaps a feeling of security which will be misplaced. I refer to land I know is subject to flood and opened same rather than that resting under the protection of any man-built bank. “SECRET PROCEEDINGS.” NAPIER COUNCILLORS’ HASTY MOVE. DWELL ARMED WITH EXHDENCE.” “The whole thing has been carried out secretly,” stated Cr. W. G. Martin at the meeting of the Napier Bor ough Council last evening when referring to the Rivers Investigation Committeess activities. Cr. P. F. Higgins stated that tho committee had touched on two veiy important schemes which might be a great menace to Napier. “It has been a secret. There was no notice given that it was going to consider “The Pines’ Scheme” he said upon explaining that the question had been discussed by several representatives of the local bodies in Napier on Saturday and yesterday when it was decided, subject to the approval of tho council, that Cr J. C. Bryant and himself arm themselves with evidence for tho committee’s sitting in Napier. “We are well armed with evidence” he added. “The first I knew of it was tonight when 1 saw in tho papers that it was open to the press ” commented the Mayor. It was decided that the engineer and the two councillors mentioned give evidence.