C—ll

REPORT Since the last report was published the Chief Drainage Engineer has retired, and by arrangement the duties carried out by him in the past are now discharged by the Ministry of Works, which has supplied the information on which this report is based. This year has been exceptionally satisfactory for drainage, apart from some flooding at the beginning of the year from the Whakatane River. The Rangitaiki River did not overflow, although on one occasion it was considered necessary to send out warning. The rainfall for the year ended 31st March as gauged at Thornton was down to 35*75 in., the average yearly rainfall being about 52 in. Rain fell on 73 days. The wettest month was June with 6*67 in. and the driest January with 0-64 in. Production figures for the Rangitaiki Plains district have continued to increase in spite of the phenomenally dry year. For the year ended 31st March, 1949, 5,387 tons of butter were manufactured, and for the year ended 31st March, 1950, the figure increased to 5,716 tons. With a minimum of storm damage this year it has been possible to catch up on arrears of maintenance work. Widening and deepening has been carried out in many channels which have been badly silted as the result of subsidence causing the grades to flatten in the low country. Four drag-line excavators have been employed on this work, one of these being out of action for six months awaiting spares. The total length of drains and canals covered by these machines during the year was 21 miles 65 chains, and in this distance 90,960 cubic yards of material was removed. A fifth machine was employed continuously on the reconstruction of the Tarawera River stop-bank. The practice of letting contracts for hand cleaning and removal of growth from the smaller drains was continued this year. The year's total for this work was 81 miles 16 chains. Each year a few more of these drains have to be cleaned by machines, as suitable labour is not available, and the necessary widening makes the drain crosssections too large for hand work. While the past dry year has assisted in catching up on maintenance work, the continued low water-levels have increased the growth of weeds, which had to be removed from waterways. Water hyacinth growth which had taken hold in two of the main canals was completely removed during the year. The efforts in the two preceding years when part-removal and chemicals were employed barely succeeded in preventing an increase in the following year. Success was only obtained by complete removal of all plants from the water. Drag-line machines were used to drag out the main bulk of plants. This was followed up by men working in a boat and on the banks with rakes. Even when apparent removal seemed complete, it was necessary to follow up with monthly patrols by boat in order to get any plants which had remained hidden in grasses at the waters edge. Over 8 miles of affected channel were dealt with. Progress has been made with the RB. 19 drag-line excavator on the reconstruction of the left bank of the Tarawera River, 73 chains being completed during the year. Along the right bank of the Rangitaiki River between Edgecumbe and Thornton a number of low places in the small stop-bank were made up to regular level. This bank will not prevent a major flood from spilling over, but is a safeguard against medium rises which occur more frequently. Some investigation was carried out prior to attempting to cut the mouth of the Rangitaiki River through the sandspit which has extended considerably in recent years, with the result that the main drainage discharge at Thornton has deteriorated. The investigation has shown that the gradual building up of the sea-bed opposite the original cut has destroyed any chances of success with a simple cut as has been done in the past. Plans are being prepared to construct a suitable training-wall to maintain the mouth at the proper point.

2