HAWKE'S BAY RIVERS.

Dominion, Volume 4, Issue 1203, 11 August 1911, Page 3

HAWKE'S BAY RIVERS.

THE PREVENTION OF FLOODS. KN'GIXKEirS REPORT. Messrs. G. Laing-Jfcason, C D. Kennedy, and J. B. Thompson, the engineers appointed by the Central Rivers' Board to report lipcm the causes of floods in the lfawlrcV- Bay district, and on Hie liot iiu'tin-i of preventing them, have presented llifir report, of which the following is a summary:—' "We consider the Tuki Tuki riverbed is at; present of •mfficirnt capacity, provided the embankments arc mniiitnini-d sufficiently, the bed kept clear of willows and erosion of (.lip bank* prevented. This is not the cass with the Nsaruroro, which from Oniahu to the sea ilows through a more or less contracted channel. " Down to that point the river is Very wide. Ihis great width causes a slackening of the current, and consequently a deposit of shingle, which will in time tend to raiso the river bed (unless the channel ;s controlled) to above the level of adjoining lands, an action which took place below Roy's Hill along its old channel previous to ISC7. Serious overflows have from timo to time occurred on oaeh side of Roy's Hill. Both these places arc now protected. On the left bank, overflows only take place in abnormal lloods. Under present conditions there does not a.pItcar to be any reason to prevent the confining of the water, iu any flood, to the present bsd within a short distance of Uinahu bridge. Thence to Pakowhai, we are of opinion that by constructing embankments at sonic distance from the river bank, clearing obstructive willow growth , and enlarging the .channel at one or. two localities, flood waters, except on very rare occasions, may bo prevented from spreading. lYom Pakowhai elowiiwards there is very little fall, several sharp bends and narrow reaches, and n most serious obstruction in the shape of the. railway .bridge, which crosses the river on the skew with a total width of less than 300 ft., and we consider it impracticable, on account of expense, lo make this portion of its channel selfcontaining and thoroughly efficient. Tru. remedy lies in providing an overflow channel, starting from the left bank about half a mile above Pakowhai.

The Tutackuri Riverbed can be made efficient to within a lew chains of I'owdrcll's crossing, From Powdrell's crossing tho disposal of the flood waters has received much consideration. Three courses present themselves —namely, (1) Through the lleanee flats and via ' the Harbour Board's low-lying laud into the Jimer Harbour, and Uience to the sea; (2). the present channel, and (3) to join the Ngaruroro overflow near NVaitangi. 'i'lie Meiuice division is longer than the other, being four and a halt miles from l'ow<lrcll's bend to the sea. We have definitely concluded that it is advisable to carry tho overflow to tho sea via Waitangi, preserving the present channel tor use ordinarily, and for the purpose of carrying a limited amount of llood water which may bo utilised for reclamation purposes. The two overflow would merge at a point about seventy chains to the enst of Brookfield's bridge. From tho mergement there would be a concentration which would be directed, with due provision for spreading for reclamation purposes, under tho_ present railway and road bridges at Waitangi. Thence, and for some distance above, the waters would bo controlled by a series of training walls to tho proposed "outlet" at the mouth of Ngaruroro River. Wo would point out that with tho exception of ono short training wall on the south sido of the Ngaruroro River it is unnecessary to do anything further in that direction, as the trend of the river is towards the north, and there will be no possibility of an outlet being forced through more to the south. As regards relative levels of discharge points for river outlets into Inner. Harbour and at mouth of Ngaruroro River wo are of opinion that when tho. suggested walls, etc., are completed at tho latter point that simultaneous readings (or levels) at both points above mentioned will show a considerable margin in favour of the position recommended for overflow by us. In order to prevent floods about Clivo and Farn'don, tho river month , must ■ receive attention; it is tho key to the whole situation. Wo consider that the comparatively small amount of additional water pru- ■ posed to bo taken that way will not only bo not injurious' to Clive, but will, with the guidance of training walls, is.uve a beneficial effect and help to maintain a good and permanent mouth. 'Jhefe training walls will absorb a large amount of the cost of our proposed works, and \vj think that the outlet works and the' two overflow channels, being of such general importance, should bo a charge on the whole river district. Necessarily the overflow proposals require tlio acquisition of certain lands for the purposes set out, and as a scheme of reclamation of adjoining lowMying lands is vory dssirab.o we recommend that further adjacent lands bo acquired by your board, or if difficulty is found iu so doing as regards tho latter, probably nn arrangement might bo made between tho owners of said land and your board, whereby "betterment" would be recouped to your board on account of reclamation. Tho area we propose that should bo bought and retained tor p;rlaaucnt overflow channel;, is approximately 818 acres, and we are of opinion that a very largo portion of this area could be leased for grazing purposes at such a rental as would provide the annual interest payable on account of purchase of same. The area to be acquired for reclamation purposes is approximately 183G acres, tho increased value ot tins area being estimated at about £lo per aero as the result of reclamation, thus showing a profit of about .£28,29(1. Hereunder summarised is the complete estimated cost of the proposed scheme, which is JCSj,4BS. including estimated,co.-t of acquiring the necessary lands. \Y\e have shown also that tho ultimate net cost to your board will bo in. the neighbourhood of £55,015, which sum is arrived at by taking credit for sale of surplus and reclaimed lands:— Total Estimated Cost of Works. Dr. £ Outlet training-walls and protective work; • "r'""ll Xgnrnroro overflow >,Vw Tutaokuri overflow UfioV Tulti Tuki River works 1,450 MutUv Civic works «i Tutaclcuri-Waimale Stream improvements 3"0 Ngaruroro River works 12,750 Old Ngaruroro River improvements ' 300 Tutaekuri River w;orks I.iUO Contingencies possible extra works, etc. 5,000 Engineering and surveying ..; 1.000 To purchase 818 acres of laud for overflow channel M.GOO Cr. By value added to 18S6 acres of land by reclamation and not required for overflow purposes at ,Cl 5 per acre, say , 25,290 By sale of 1G acres of surplus land, 29,140 Net ultimate cost of works 55,045 Dr. balance .£85,455 The Rivers Board have considered and approved the report, and havo decided lo .rnipe a loan, with :in advance'of .£IO,OOO, for immediate work.