FLOOD CONTROL.

Manawatu Herald, Volume XLVIII, Issue 3544, 30 September 1926, Page 1

FLOOD CONTROL.

ADDITIONAL EVIDENCE. BOROUGH VIEWPOINT. ON FLOOD PROTECTION SCHEME. PALMERSTON N., Sept. 27. Following an adjournment to enable the members to obtain certain required evidence in Wellington, the Aiana-watu-Oroua River District Commission resumed its sittings this morning, when Mr Cooke called witnesses for the borough. The first was Mr W. L. Fitzherbert, one of the Borough Council’s representatives on the Palmerston North River Board, who gave evidence concerning the river protection work that had been done in the borough. Prior to the old Palmerston North-Ivairanga Board coming into existence in 1913 the expenditure, he stated, had been as follows: McCarthy’s contract with Borough Council, £2300; groyne system, Borough Council £4OOO and Government £4OOO, £8000; willow planting and river protection at Esplanade by Borough Council, £400; scour channel on right bank above Fitzherbert bridge, Kairanga County Council and Borough Council jointly, £300; total, £II,OOO. Then the old river board had spent the following sums from 1914 to 1921, the date when the new board had come into existence: 1914, £740 8s; 1915, £4649 18s; 1916, £874 13s; 1917, £1064 Is; 1918,£491 16s; 1919, £255 8s; 1920, £3Bl 8s; 1921, £339 16s. The new board’s expenditure had been: 1921, £3O 3s; 1922, £6OB ss; 1923, £416 10s; 1924, £557 17s; 1925, £2682 14s; 1926, £2661. The grand total of all the above amounts was £26,773 17s.

T,Jje present board contemplated further expenditure—upwards ' of £6OO0 —to bring about further improvement to the river. The cut that had been made at Fitzroy bend had been eminently satisfactory as far as the borough was concerned, but had affected the interests of those living on the other side of the river, with the result that further protection work would have to be carried out.

In reply to Mr Baldwin, who appeared for the Manawatu-Oroua River Board, witness stated that the Palmerston North River Board had not considered the effect its proposed works would have or. de-grading the river or the effect on the Fitzherbert bridge. • Questioned by the chairman (Mr R. M. Watson S.M.), Mr Fitzherbert stated that he, personally, thought that, if the Manawatu-Oroua River Board’s proposed works were carried out, the difficulties of the Palmerston North Board would be increased by reason of the greater velocity of the river.

At this stage, after argument with Air Cooke, the chairman expressed the view that evidence concerning the protection work that had been done in Palmerston North was not relevant to the purpose of the inquiry, but said, if counsel desired, the commission would hear it. EFFECT ON RATES. Further evidence for the borough was then given by Mr M. A. Eliott, who stated that the present rate was 7jjd in the £1 on the unimproved value. This in many quarters was thought to be too high, and,' if the borough had to find £IO,OOO for the river Board’s scheme, there would be further discontent. Personally, he thought that Palmerston North would not derive any benefit from any betterment of road facilities brought about by the carrying out of the River Board’s scheme, and the suggested stimulus to trade he regarded as very visionary. He knew that an ex-tensively-signed petition had been forwarded" to the Government to have the board abolished, and presumed that the commission was the result. The objection to the board carrying on was based on the consideration that the rates would be too high for the ratepayers to bear. He was a landowner in the board’s district, and, if the scheme would give complete immunity from flooding, it would, in his opinion, increase the value of his property by £2O per acre. But if the scheme were a failure, it would be disastrous for property-owners who had paid big rates to the board. Asked by Mr Baldwin whether Palmerston North was not a lightly rated borough, witness replied that he thought this was so. At the present time his and other properties adjoining the Oroua were at the mercy of a very slight rise in that river, as the breaks in the banks had not been repaired. It was true that the Palmerston North Borough Council was putting before the ratepayers a loan proposal in connection with the Agricultural College, the amount involved—£l9,oo0 —being the same as that asked of the borough by the River Board, but he doubted very much whether the loan would be authorised.

Replying to the chairman, witness stated that, ns a land-holder in the board's district, he did not object to the scheme, provided, of course, that it turned out successful. But, as fains Palmerston North was concerned, he did not think that much benefit would accrue; in any case he thought it would be impossible to assess the benefit, which he thought would he very vague. QUESTION OF RATES.

Mr Cooke then called Air D. Buchanan, of Tiakitnhuna, to give evidence on behalf of the Alanawatu Ratepayers’ Association. Witness, on oath, gave particulars concerning the effect in his district of the recent flood. He did not think that the Makerua Board’s banks had done him any harm. He was one of those who had signed the petition praying, for the abolition of the Manawatu-Oroua Board his objection being based on the ground that the rates he would have to pay would not be commensurate with the benefit he would receive. Mr Baldwin: Don’t you know that, if your land will not receive benefit, it will not bo rated? Witness: No. And won’t that affect your attitude? —Yes. if I am not rated. Afr E. AVood, chairman of the Alanawatu Drainage Board for the past 12 years, gave evidence on behalf of that body. Tt was his board’s object, he stated, to do all work as far as possible out of rates. He did not think that the Alanawatu-Oroua Board’s project would benefit his board, or that the ratepayers would be able to bear the cost.

At this stage the commission adjourned for lunch.

OPPOSITION EXPRESSED

BY DISTRICT DRAINAGE

BOARDS

PALMERSTON N., Sept. 28. On the resumption of the sitting of the Manawatu-Oroua River District Commission yesterday afternoon, Mr E Wood, chairman of the Manawatu Drainage Board, continuing his evidence, stated that the recent big flood had not cost his board more than £^U. Replying to Mr Baldwin, who appeared for the Manawatu-Oroua River Board, witness stated that the extra fall at the month of Burkes drain that would result with the carrying out of the board s scheme would not be sufficient to give any material benefit. His board very much obiected to the amount it was expected to contribute towards the scheme. The chairman (Mr R. M. Watson, S.M.): But your board would welcome anything that would give 1 re Certainly, if we don’t have to nav. (Laughter). . Mr‘Baldwin: It is entirely a question of financial responsibility. Further questioned by Mr Baldwin, witness stated that his board would too great a height above the country Oroua river, but this, he declared, '“"'evidence'foi! foxton. Air Bergin, on behalf of the Foxton Borough Council, Harbour Board and Moutoa Drainage Board, then called Mr J. Chrystall, ev-Mayor of Foxton, who in evidence, stated that, as fai as the Moutoa Drainage Board was concerned, a resolution had be passed objecting to the River Board s scheme on the ground that it would be of no benefit to witness s board, but would be rather of a detriment. If the scheme were carried out, there would be, for several years, great dislocation to the Moutoa drainage system, and he thought that compensation should be allowed his board Makerua had obtained immunity only at the expense of other drainage boards; and he wished to point out that Makerua’s safety depended only on Moutoa not banking. If his board were to bank just one foot higher than Makerua, the district m the latter board’s territory would again be subject to flooding., If the River Board s scheme were carried put, the cut through the Moutoa district woul take out of productivity much valuable land, and the compensation that would, have to be paid to owners would considerably add to the cost ot the scheme. It was his opinion that, if the scheme were to be carried out, the work should be prosecuted by the Government and not the River Board, as a guarantee that it would be completed and the ratepayers would not be saddled with any additional costs that might crop, up when they were already rated to the full extent or their capacity to pay- M ith regard to the attitude of the borough, there w f as again a decided objection to the board’s scheme, which, if carried out, would necessitate the reorganisation of the sewerage system owing to the fact that the septic tank would be deprived of its outlet. He did not think that Foxton would ever become a port of any considerable dimension, but, it there were any guarantee of "'creased shipping, he thought that the iiaibour Board would not object to paying a rate to the River Board. However, he did not think that much ot an increase in shipping would ever come Questioned by Mr Innes, witness stated that, as a farmer, he strongly objected to any alteration in the river, quite irrespective of any question of cost. That opinion, he thought, represented the attitude of the majoiity of the Ratepayers in the Moutoa. In replv to Mr Cooke, witness stated that he was not one of the signatories to the petition to abolish the River Board, but this was only by reason ot the fact that he had not been approached. '‘l am sorry that the petition was not successful,” added witne|lr Cooke: Do you think that the scheme will in any way benefit the bar at the mouth of the Manawatu ? AVitness: No. . ...... To Mr Baldwin, witness stated that he would rather have additional banking in the Moutoa than the Riy®* Board’s scheme. He did not think that the district could afford to pay more than £IOO,OOO, plus maintenance, if the scheme were gone on with. „ ~ The last witness for the afternoon was Mr D. Rowland, of Tiakitalnina, who gave evidence that the 1902 flood had been 3ft. 6ins. higher at his house than the recent one. Since 1898 about 60 acres on his property had been washed away, about half the area. The commission then adjourned till this morning. BASED ON SOUND ENGINEERING PRINCIPLES. APPROVAL OF PUBLIC WORKS DEPARTMENT. PALMERSTON N., Sept. 29. “I believe that the scheme proposed is the one which accomplishes the desired purpose with the most reasonable amount of expenditure without unduly exceeding the benefits to be obtained from the scheme. In other words, it is the only scheme that is financially possible. On account of this and because it is a reasonably safe scheme based on sound engineering principles of flood control, the Public Works Department will be prepared to give the scheme its approval should such become necessary,” stated Mr John Aloud, inspecting engineer for the Public Works Department, when giving evidence before the Manawatu-Oroua River Board Commission this morning. “CAREFULLY THOUGHT OUT.” “I find,” continued Air Wood, “that the scheme proposed by Mr F. C. Hay has been most carefully thought out and has been designed in accordance with the recognised practices of flood control. The main object of flood control is to exclude flood water from the land. This * s provided for by the construction of levees at a suitable distance apart to confine the water at high stages of flow. In the case of the Manawatu liver, it is not possible to confine the existing river without constructing banks of dangerous height and of prohibitive cost. It is at once apparent that, if flood waters are to be passed to the sea at an economical cost, some scheme must be adopted that will necessitate reasonable sized stopbanks. To obtain this the flood water heights must be reduced. Mr Hay has done this by making a cut off and relief channel, thereby increasing the velocity of the flood water and the cross-sec-tional area of the waterway. Allowing for tlie present channel carrying at first flood water to its full channel capacity, which it will undoubtedly do, and the provision of a cut off channel with a waterway of 1300 feet in width. I find that slightly more than 100,000 cusecs can he safely discharged to the sea. This is a flood that appears likely to occur every ten years.

PROVIDING FOR FLOODS. “To provide for the passage of greater floods, Mr Hay has assumed that fairly rapid de-grading and widening of the channel of the out will take place and that ultimately this channel will carry a flood ten per cent, greater -than the greatest flood of which wo have any record. The velocity of the flood water in the cut is sufficient in my opinion to cause scouring in this.channel at_ a more or less rapid rate depending upon the frequency and magnitude of the floods. The success of the scheme, if this de-grading and erosion takes place, as I anticipate, will be assured

within a reasonable number of years, and increased protection will be obtained year by year until the channel is of sufficient capacity to pass a maximum flood. ... It is simply a question of balancing high initial costs against a reasonable risk and an economical scheme of protection. Protection may easily be bought at a cost much beyond the ability of the community to pay.” FEASIBILITY AND COST. Dealing with the main points that had arisen in connection with the feasibility and cost of the scheme, Air Wood stated .that he considered sufficient velocity of flood water would be obtained in the proposed cuts to bring the new channel within a reasonably short period into a satisfactory river channel of sufficient capacity to carry off safely the floods of the Manawatu river. He was strongly of the opinion that no greater width than 1300 feet should be adopted. He was sure that a wider channel would cause deposition of silt that would not only cause the channel to meander and erode its banks, hut would also keep the river at to be protected. De gradation in the river bed above the proposed cuts would undoubtedly take place, but to what extent it was difficult to predict with any degree of accuracy. The effect that the increased flood slopes occasioned by de-gradation would have on the shingle deposits in the river in the higher reaches was hard to estimate, but he believed that the shortening of the river and the consequent increase in slope of the flood water would result in shingle being carried down to a point well below the junction of the Manawatu and Oroua livers, and the shifting downstream of this shingle would undoubtedly have the effect of checking the otherwise heavy de-gradation that would occur above this point. It seemed certain that the shingle would be ground to sand bv the time it reached the upper end ot the new cuts through the Moutoa, and that it would consist of larger and larger particles as one advanced up the river. LOWERING FLOOD LEVEL. “From certain well-known principles of hydraulics pertaining to river discharge,” proceeded Air Wood, . have computed that the flood leve, just above the Alannwatu river s junction with the Oroua should, as a result of the proposed cut, be lowered something like five feet. It will possibly be somewhat greater than this at certain stages, but I think the grade from here on will be steep enough to keep the depth at about this mark by aggradation from shingle transportation. From this point upstream, 1 believe the de-gradation will become less and less until we reach a point a mile or two above the burn bridge, where wo may not anticipate a lowering of the river bed by more than one or two feet, but 1 doubt very much if it will reach this amount, ‘While I believe the River Board’s scheme will cause de-gradation and erosion at a sufficiently rapid rate to give, within a reasonable time, a good waterway for floods, T do not think wo need fear the effects ol an excessive degrading. PROTECTION REQUIRED. ‘'With regard to the protection required to cope with the increased velocity of the river within its shortened course, I am not of the opinion that protection of a very costly nature wili be necessary. . . . To cope with even maximum flood velocities, however, I consider that protection by short spur groynes with strong heads at intervals of ten to twenty chains and willow and other tree planting, will bo adequate. Such a protection will not be necessary at once, and its cost will have to be spread over a number of years. For this reason an adequate amount of money raised by rates appears to me to be the best way oi meeting the cost ol this work. From my experiences ol river protection at the velocities to be expected in the improved channel, I think a suitable protection could bo obtained at a cost oi about £4OOO per mile or a total cost ol £60,000 to £70,000. It is likely that this cost would be spread over a period of 15 to 20 years. • COST OF THE WORKS.

“AVith reference to tlie cost of the works proposed, I have gone carefully into this matter. Air Hannah, of the Public AVorks Department, has checked over the quantities in the proposed scheme and has found that they are on the liberal side. Mr Hay, in addition to this, has added 25 per cent, on to his earthwork quantities. This, in itself, should give a margin to cope with any immediate protective works required after the main work is completed. but it is, of course, safer to assume, as has been done, that it will be required to complete the levees. “I consider that £450,000 should satisfactorily complete the whole of the works proposed, assuming that so much as is necessary to Air Hay’s scheme of tlie Alakerua Drainage Board’s works already constructed is taken over by the River Board. That is to say that the £450,000 is above the cost of such works. I agree with the principle (adopted in the board’s scheme) that the future protective works be carried out by an additional rate over and above that required to meet interest and sinking fund. IMPROVING f THE HIGHWAY. “AA T ith reference to the . suggested improvement of the main highway between Koputaroa and Palmerston North, there is no doubt that, by preventing flood waters from the Atanawatu river spreading over the adjoining low country, it would be possible to construct a main highway on a much better location than the present one between these places. It will be possible to get a road not only four miles shorter, nut also one that will be practically level the whole way,” concluded Mr Wood. Questioned by Air Cooke, witness stated that, undoubtedly a big flood during the course of construction work would do a lot of damage. It was impossible for only part of Air Hay’s scheme to be done at first. OPPOSITION TO SCHEME. On oath, Mr P. Nielsen said he had acted as secretary of the Manawatu Ratepayers’ Association since the inception of that body and had been instrumental in securing signatures to the petition praying for the aboltion of the board. Of the 449 ratepayers on the board’s roll at that time, 173 had signed the petition, and undoubtedly

more signatures could have been obtained if time had permitted. Only five or six refusals had been forthcoming. The valuation of the board s area at tlie time when tlie petition liad been prepared had been £2,986,590, of which amount £1,575.752-had represented the value of the signatories’ holdings. Questioned by Air Baldwin, who appeared for the board, witness admitted that his association had no corporate status. He would not contradict counsel if lie were to assert that two-thirds of the signatories were in the nonratepaying class. He admitted that the petition had been signed prior to tlie last flood and that several of the signatories had given evidence before the commission in favour of the board’s scheme. SETTLERS’ EVIDENCE. The next witness was Air P. G. Mildon, a member of the Kairanga County Council, who contradicted a statement made to the effect that the council was in favour of the River Board’s scheme provided that tlie board would take over the Taonui and Alangaone stveams. The council, added witness had no jurisdiction over these two streams, which were under the control of tlie Alannwatu Drainage Board. , , r T AVitness, in reply to Mr Innes, stated that his property was not included in tlie board’s area. Questioned by Air Baldwin, witness admitted that his property drained into Taonui. . . Additional evidence was given by Air R. Murphy, chairman of the Sluggish River Drainage Board, who stated that that body was against the .River Board’s scheme with the exception ot one member, who occupied a seat on both hoards. The Commission then adjourned for lunch.