THE Hauraki Plains Gazette With which is incorporated THE OHINEMURI GAZETTE. Motto : Public Service. MONDAY. WEDNESDAY. & FRIDAY. FRIDAY, JUNE 1, 1923. FLOOD PROTECTION.

Hauraki Plains Gazette, Volume XXXIV, Issue 4571, 1 June 1923, Page 2

THE Hauraki Plains Gazette With which is incorporated THE OHINEMURI GAZETTE. Motto : Public Service. MONDAY. WEDNESDAY. & FRIDAY. FRIDAY, JUNE 1, 1923. FLOOD PROTECTION.

The recent floods throughout the Dominion have caused many people to ponder on the problem of protection from floods. The Tajeri River, in Otago, which was considered to be well a>nd adequately stop-banked, recently broke through the banks on two occasions, flooding the Taieri Plains, and doing an enormous amount of damage. The town of Blenheim, which in former years was subject, to periodical flooding from the Wairau and Omaka rivers,, has been free from floods for many years past in consequence of the stop-banking of those rivers. During the recent, heavy rains those stop-banks broke, and a most disastrous flood has done an enormous amount of damage to the town, the water in some instances having been breast-high in the streets. These are two only of the instances of recent flood damage, but they are sufficient to make a person think of what the probabilities may be in our own district, and what the effect may be if any of the stop-banks now being erected on the Ohinemuri and Waihou rivers should fail in. time of flood and the huge volume of water confined between the banks should be released. In the past the flood waters of the Ohinemuri River 'have overflowed at Moananui’s Bend and gone across country between Paeroa and Tirohia t,o meet the Waihou River. With this great volume of flood water confined by the stop-bank at present being erected on the south bank of the Ohinemuri River, that water must now ceme down the river channel t,o meet the Waihou at the junction. In the past about 25,000' cubic feet per second of flood waters of the Waihou River have found their was across country at Awaiti, and been absorbed in the swamps and the Awaiti Stream and Piako Riven. With the st.op-banking of the upper Waihou that water must now come down to the Puke, to mingle with the flood waters of the Ohinemuri River. The Public Works Department in its calculations has allowed for 29,000 cubic feet per second from t,he Ohinemuri and 9000 cubic feet per second from the Waihou, a tot,al of 38,000 cubic feet, for which provision must be made at Ngahina Bridge at the Puke, and with the added water, from the

Komata Creek and other tributaries this amount will be increased to 41,000 cubic feet per second at Waimarie Bend. The pi esent condition of the Waihou Riv< r channel between Ngahina Bridge and Waimarie Bend is capable of canning only 10,000 cubic feet. To provide for the additional 31,000 cubic feet which the river will have to carry in time of flood great stop-banks are now being constructed. Experience elsewhere makes one realise what, is likely to happen to the country around Paeroa and down to Hikutaia and beyond if those stop-banks gave way. The Public Works Department forecasts this contingency, with the result that, the st, op-banks will be of such a dimension as to ensure safety, but this can only be at an enormous cost, which the district will have to bear later, on, when the works are completed, and even then the experience on the Taieri Plains'shows that the work of man cannot, always stand against the forces of Nature. In view of reducing the enormous cost M'r, R. W. Holmes, the Engineer-in-Chief in 1917, recommended that a cut be put through from Waimarie Bend to the mouth of the Hikutaia Creek, to allow for the free get-away of flood water, and doing away wit,h the heavy cost of the great stop-banks that would otherwise be required. This recommendation met with considerable opposition from those whose lands the cut would go through, and in January, 1918, an independent report was obtained from Mr Blair Mason on the proposal. Mr Blair Mason, after a careful study of .all available data and the local ’conditions, strongly advocated the proposed cut. in his report he pointed out that it would increase the tidal capacity of the Waihou River above Hikutaia by at least, one-fourth, thus ensuring a greater scouring effect and keeping the channel open- in normal times, and that the increase in tidal capacity above the proposed cut would proportionately increase the tidal velocity, with results that could only be beneficial and with a tendency to increase the depth of the ilveT, and at ebb half tide would give an increased capacity of 14i30 cubic feet per second. Further advantages pointed out were that the eour.se of t,he river would be shortened I?y four miles, that the fall between Puke and the sea would be increased, thus permitting the flood wateijS to get away more rapidly, that there would be an increased velocity at Hikutaia of three feet per second, and high water at the Junction would be twenty-eight minutes earlier than at present, The increase in tidal capacity above the proposed cut is calculated at 37 million cubic feet. With this enormous volume going seawards in normal times of ebb tide the'effect can only be to keep the river clear of shoaling up with the silt, and river sands that are brought down and deposited in the bed. One of the reasons of objection to the proposed cut was that itwould isolate Netherton from the river traffic, and materially prejudice the drainage of. the lands in that district. but- a perusal of the report of the Engineer-in-Chief shows that the fear of that is groundless, as he recommends the construction of a road across the Waihou where it would be dammed up to turn t,he river -into the cut, making ample provision for adequate - drainage of the district, and points out that when the PaeroaPokeno' railway is constructed there will be a station near Neffi er t° n ,. anc * that tjie location o£ roads be amended to suit the altered conditions with the object of securing proper access, and that full compensation be paid to all persons from whom land is taken for the purposes mentioned. The recent floods in the district have again turned attention to this important project, with the result, we undersand, that it is to be brought up for discussion at the next meeting of the Chamber of Commerce. Recent inquiries on the matter show that If the proposed cut was put in the stopbanks on the upper Waihou could with safety be reduced by two feet in height, that the stop-banks below Ngahina could be reduced in height and width, and the great length of stop-bank would not be necessary around Waimarie Bend. The saving in cost would amount to many thousands of pounds, which is a matter; well worthy of conside'ratiop when it is known that the cost must ultimately be borne and paid by the residents in the district, and the works would be completed some years earlier than is likely to be the case at present. The putting in of the cut will no doubt involve some recasting of the present scheme of works of the Department, but with the plans and data already available that is a small matter, and withdrawal of all opposition to the proposed cut would no doubt, be welcomed by the Department as affording it an opportunity to put into effect the recommendations of some of the most, able authorities in the Dominion, including Mr Furkert, the present Engineer-in-Chief. Speaking with an old resident of this locality, and one who was in a position to observe the river during the recent flood, he said that he was cue who signed the petition against the. Waimarie cut going through, but he was now satisfied that the day will come when this work will have to be done.