LAND DRAINAGE

Bay of Plenty Beacon, Volume 1, Issue 55, 28 August 1939, Page 8

LAND DRAINAGE

WORK ON THE RANGITAIKI REPORT FOR THE YEAR The unusual Avcather conditions of the past season have been responsible for a general decline in farm production in which the Rangitaiki district ha s participated. A rainfall of OA r er loin, in February, 1938 Avas folloAVed by a Avct autumn and Avintcr on the Rangitaiki Plains. The following summer Avas unusually dry, and in March ,1939 the rainfall Avas only half an inch. These extremes of Avet and dry Aveathcr have affected the pastures and reduced the returns of the settlers says the annual report of the chief drainage engineer, Mr R. L. Innis. The quantity of butter manufactured by the Rangiaiki Plains Dairy Co, Avhich handles a large portion of the dairy produce of the Avas 4256 tons for the fiscal year ending 31st March, 19.39, a decrease of 437 tons on the'output for last year. The rainfall at Thornton, for the period of 12 months April, 1938, to 31st March, 1939 ? inclusive, avas 51.10 in. Rain fell on 124 days. The Avettest month Avas July, Avith a fall of 11.13 in and the driest month Ava? March, Avhen the rainfall Avas 0.55 in. The aA'erage rainfall for the past twenty-one years has been 52,9 in. The programme of maintenance dredging of the main drainage cr.oals Avhich Avas commenced last year has been continued and a new light drag-line excaA'ator has recently been added to the plant to be employed on the AA'ork. Good progress has been made with the Avork of raising the stopbanks on the right bank of the Tarawcra RiAcr but the unsatisfactory condition of the stopbank on the left bank of this river has caused anxiety. Two serious breaks in tlvs stopbank occurred during the Avinter. and either of these breaks c ould haA'e been the cause of the river leaA'ing its present course. The construction of the stopbank on the left side of the river Avas not part of the Rangitaiki Drainage Scheme, and the bank is not maintained. The bed of the Tarawera River is above the level of the land lying between the riA'er and the Avcstern hills, and the soil of the. river bank is easily eroded pumice sand. Originally Hie OA'erflow during floods Avas of shallow depth and distributed along seA'eral miles of' bank. Noaa* Avhen the inadequate stopbank breaks, flood wntor passes through the breach w'tli considerable volume and Aeloeity, and should the efforts to close one of these breaks fail the resulting flooding may cause loss of stock and disorganisation of road and rail com. munication Avithin, the district, and it may prove A T ery d'fficult to return the river to its original course. Tins matter is of sufficient importance to warrant early attention. Legislation passed last session giA'cs the Minister of Lands power to prohibit the construction of drains Avhere they cause seepage under the Tarawcra stopbanks. In this connection for their protection the settlers on the riA'er banks should communicate with the Drainage Office at Thornton before constructing any drains Avithin a distance of 5 chains from the TaraAvera River stopbanks. DREDGES. No. 17 Monighan dragline excaA-a. tor after completing 48 chains of nurntenance dredging in Rcid's Cen tral Drain, commenced the deepening of the Kopeopeo Canal and at the en t ] of the year had completed 182 chains between the junction of field's Central Drain and a point 14 chains cast of the Eastern Road bridge. This machine excavnt-d approximately 84 700 cub : c yards of material during the year. No. 30 Bay City dragline excaA'ator Avas engaged in raising the eastern Tarawera stopbanks during April and May. Tn June the machine AA'as transferred to the western bank of the riA'er to. repair breaks in the stopbank, and was engaged on th's wo'k and impro\-ing 100 chains of Withy's drain and 12 chains of the Upper Awakaponga until o:tibcr, when, after (wcrhaul it resumed work on the eastern stopbanks. Approximately 56,400 cub'c yards of material Avas placed in, raising this stopbank for u distance of J66 chains d)c»ve the railway bridge. The total uitput for this machine Avas approximately 62,100 cubic yards for the year. No. 28 light Bay City dragline Avas overhauled in April and between May and October Avas engaged r naintenanee Avork on the Rangitaiki, Fa'awera and Whakatan? RiA'ers. Since NoA'ember this machine has been used for driving sheet nil'n-.T

and other work iri connection with the Orini llood gate. The material excavated by this machine was 9400 cubic yards. No. 32 light Diesel dragline cxcava tor commenced work in March 1939 and constructed 11 chains of stopbank at the upper end of the Man: garoa Drain. This machine, which operates a 3-8 cubic yard bucket on 30ft boom, should prove an extreme ly useful addition to the excavating plant'. FLOOD GATES. A large outlet structure, comprising three 5-ft diameter flood gates, was commenced in, the mouth of the Orini Canal on the left bank of the Whakatane River in 1938. When completed these flood gates will exclude tidal water from the drainage system of the low-lying area at the north-eastern corner of the district. A 4ft diameter flood gate is under construction on the' Omelieu Canal to provide an additional outlet for the Omelieu Settlement. A 4ft diameter flood gate has been constructed on the Kopeopeo Canal, and a similar structure at the northern end of the eastern drain. Also one llood gate of 4ft diameter and one of 3ft diameter have been completed on the Omeheu Canal. A working party of three to five men has been engaged with a tractor throughout the year removing willows from the banks of the Rangitaiki River and the channel has now been improved in this manner from Thornton to Edgecumbe, and the willows have been ring-barked for a further distance upstream. Dining the year 362 chains of river-bank was cleared of willows, and the trees after being cut into convenient sizes have been stacked on the river bank for burning. Tn June, after two unsuccessful attempts, the mouth of the Rangi. taiki River was opened in the line of the river's direct approach to the sea and, though the new mouth has subsequently moved about 15 chains conditions have been favourable for the drainage of the lowlying land along the lower reaches of the river. TAIIAWERA RlVl-li. In addition to the work carried out in connection with raking and repair of stopbanks upstream from the railway bridge mentioned above, the right stopbank has been raised for a distance of 9 chains upstream from the Whakatanc.Tauranga Main, High way bridge. The boulrler groynes and other training Avorks for fixing the riA'er mouth completed la-'t year haA'e produced excellent results. MAINTENANCE. Tn addition to the remoA'al of silt from the large drainage channels with mechanical exeaA'ators, a Aveedcutting launch is used for removing aquatic growth from the Avaterways, and a A'cry considerable mileage (if smaller drains is cleaned annuallj' by manual labour. The receipts and payments account, for the year showed on the receipt side that rates amounted to £13,226 1s 4d. rents £172 6s 7d, IaAV costs £54 4s 4d subsidy on maintenance costs £2409' 2s 3d, sundries £2495 17s 2d, transfer of expenditure to treasuty adjustment account £9561 1s lid, making a total of £27,918' Is lid. On the payment side of the balance sheet maintenance completed Avorks was £9561 Is lid, refund rates £155 8s 10d ? transfer net receipts to treasury- adjustment account £18,202 2s lOd.