FLOOD PROTECTION.

New Zealand Herald, Volume LVII, Issue 17486, 2 June 1920, Page 7

FLOOD PROTECTION.

— -"O— , '-Jj WAIHOU' RIVER MENACE.'* • REPORT OF COMMISSION. DREDGING AND STOP-BANKS. , [BT TELEGRAPH. OWN" C'ORHESI'ON'DEXT.] PAEROA, Tuesday. | The report of the Royal Commission r set U P las» October to inquire into the j question of flood control in the Waifcou River was read at. meeting of delegate# | of local bodies constituting the Thames f j Drainage Reference Board, held at ' Paeroa. Mr. E. W. Porritt acted ;,s chairman. I The report was a very lengthy one, the • principal points being as follows:—The portions of the Waihou River inspected by the commissioners comprised the lower j 3 Waihou, between Ngahina and Hikiitaia > and the adjacent lands, the upper Waiaou r from Tirohia to Ngaaina and the con- ' et ruction works ; n progress. Ohinet muri River from Pacru. u, Waihi was ! also inspected. In preparing their leport the commissioners had before them . the evidence given in 1910 before the Wai- \ hou and Ohinemuri River Commissi™, ! also all available data: on the subject in the possession of the Public Works Department. The Meteorological Depm- j ment supplied the Commission with particulars of the rainfall during all the large j , rtems of the past 20 years. Regardiiv i the value of the lands afiected bv floo-j" no information is available, and the commission had to sift the evidence given in , 1910 ln - order to arrive at a fair average value of such lands. The commissioners j went ve.ty carefully into the economic side of the (question, and concluded 'h?.t what might with justice be expended < n flood control below Ngahina was strictly limited, otherwise tho annual charges for interest, maintenance, etc.. would "exceed the monetary_ benefits -which might be derived from immunity from flooding. At tho same time it was considered that works adequate to control the largest flood i, likely to be experienced within a period 1 of 50 years can be' constructed at a cost not in excess of what the land can reason- . ably carry. ■ Partial ! - i?ro?ection Ssseaiml. The view m held by the commissioners that whatever the character of the Ulti- i mate work*, partial protection, namely, protection against medium floods shorid ( be provided as early as possible, especially as this can generally be done without- unduly, if at all, increasing the ultimate ; ' cost of any complete scheme for dealing ! with larger floods. The report points i out that for 6ome distance below the Ngahina Bridge the present channel wit'i- , out overflowing its banks would not ac- ' commodate more than 25 per cent, of the maximum flood discharge, and for some i j 12 miles has only about ;50 per cent, of ! tho required discharging capacity. This j \ can be increased either by dredging the *' ; channel, by building levoeii to enclose the - i flood water, or by a combination of the two methods. . The Commission is of opinion "that the I improvement of the river from fhe sei to Paeroa, and the maintenance of Hie j channel,_ is of supreme importance to 'he ! whole district. No scheme for river con- - trol below Ngahina should be entertained I which does not embody this feature. Combined Methods Advocated, i | The commissioners conclude that a com- "R? biflation of dredging and stop-banking vr 11 •' | be the best system of flood control. They | recommend that very temporary step- * banks be constructed on both sides of the ■ 1 river. These would give partial protec- If tion at the earliest possible date, and | would form part of the final banks. As 1 the essence of the recommendations-is {ho ~ \ provision of rapid temporary protection. ? all available ploughs and scoops should be E started at the down-stream end on ♦ho P low banks, and two steam shovels should I? be ordered at once by cable. This wk ' should easily bo completed in two years j provided that the steam shovels are de- - livered within six months. The witnesses I who appeared, before the Commission I offered to give, free, of cost, the land. for I the 6top-banks if, these were placed as % J suggested in. the report. The Com- | mission recommends _ that the ' worst of | the shoals in the river bo removed bv if dredging, not only in the interests of f navigation but fcacav.se these' shoaLfaic 1 obstacles to the fee flow of flood paters. a The Government's Schemes. ; I The Commission also reports on t'.s . 1 schemes which have been devised by lb* ■ •|t Public Works Department to prevent • I flooding. They consider that the 'De- § partment was not justified in' assuming ,? §j that the whole of the work of flood con- 1 trol should be carried out by stop-bank- jjl ing, instead of by a combination of dredg- l] ing and banians, the latter being a more •II eoonomivaj system. The commissioners I obtained no definite information as to ; a when the Department proposes' to com- §J plete the works, but they judge from past • j progress that the time will be longer than 1 A it would be reasonable to expect the hurl- a owners to wait. ' || After the report had been read and di:-- *|j cussed the meeting decided to advise the '.{ Public Works Department' that tho board ,f approved of the Commissnon's finding and ' -J to ask the Minister for Public Works wh it . tj steps 'have been taken to carry out the " jjrj] Commission's recommendations. •■" * / -||j