C.-ll

1938. NEW ZEALAND.

DEPARTMENT OF LANDS AND SURVEY. RANGITAIKI LAND DRAINAGE. REPORT FOR THE YEAR ENDED 31st MARCH, 1938, TOGETHER WITH STATEMENTS OF ACCOUNTS.

Presented to both Houses of the General Assembly in pursuance of Section 10 of the Rangitaiki Land Drainage Act, 1910.

Sir.— Department of Lands and Survey, Wellington, Ist June, 1938. I have the honour to submit herewith the report of the Land Drainage Engineer on drainage operations in the Rangitaiki Plains for the year ended 31st March, 1938, pursuant to the provisions of the Rangitaiki Land Drainage Act, 1910. I have, &c., W. Robertson, Under-Secretary for Lands. The Hon. Frank Langstone, Minister of Lands.

REPORT OF LAND DRAINAGE ENGINEER. Sir, — In accordance with the provisions of the Rangitaiki Land Drainage Act, 1910, I have the honour to submit the report on the works for the year ending 31st March, 1938. Although last season was generally classed as being not favourable to dairying, the Rangitaiki Plains came through remarkably well. On certain of the lighter lands the pastures were affected by the dry conditions, but generally the drained and grassed swamp lands were suited by the prolonged periods of low rainfall, and the dry conditions were favourable to cultivation and drainage improvement. Following the dry spell, exceptionally heavy rainfall, totalling 15 in. for the month, caused flooding in the rivers, with an overflow of the Whakatane River into the White Pine Bush area and minor flooding on several other areas, with the usual pasture damage which results from a summer flood. The prevention of flooding of this nature is one of the most difficult problems on this or any other drainage area, and in many cases must be accepted as the risk attendant on the farming of swamp lands, particularly where these are only a few feet above sea-level. On the Rangitaiki Plains, fortunately, the soil is of a free-draining nature and the land readily responds to cultivation after the passage of the flood waters. A commencement was made during the year with a programme of maintenance dredging of the main outfalls in the area, the Monighan dredge previously employed being thoroughly reconditioned for this work. This plant started work on the eastern district. A light drag-line plant was also employed continuously on the smaller canals and drains. The result of this work will be to give the added depth made desirable by the subsidence of the country and will also allow for the freer passage of flood-waters. Extensive groyne work was carried out at the mouth of the Tarawera River to prevent the channel widening and shoaling beyond a safe point. This work has been successful in providing in addition a slightly lower water-level in the lower levels of the river. Dredging of the river to provide spoil for the raising of the east bank stop-bank was proceeded with throughout the year. On the completed section where the banks are fenced against stock there is now a reasonably safe protection. As previously emphasized, the river flowing at a considerably higher level than the land exerts a constant and considerable pressure on the loose understrata of the banks, and it is here that the weakness lies. Every endeavour has been made to impress on settlers adjoining the river the danger attendant on the construction of drains immediately inside the banks, thereby weakening the resistance, but for the safety of the district generally it is necessary that some definite form of control of drainconstruction should be exercised.