LAND DRAINAGE SCHEME

Press, Volume LXXXII, Issue 24800, 14 February 1946, Page 4

LAND DRAINAGE SCHEME

North Canterbury Area

WORKS COSTING £165,000

A scheme for the ultimate adequate control of land drainage and flooding of a large area of North Canterbury between the Ashley and Waimakariri rivers from Oxford to the coastline, which, it is estimated, altogether would cost £165,000, has been prepared by Mr H. W. Harris, engineer to the Waimakariri River Trust. His report was received at the trust’s meeting yesterday, but as the North Canterbury Catchment Board will be taking over the trust’s responsibilities shortly, the trust decided to forward the scheme to the board for discussion with the local bodies concerned.

In his report Mr Harris estimates that the work would take from two and a half to three years to complete with adequate equipment, and would benefit an area of 94,430 acres. This area, which has a capital value of £2,630.800, would have to contribute approximately £34,300 to the cost of the scheme if the Government provided a subsidy of £3 for £l. The annual rate required to meet the area’s proportion of the total cost would be spread over a period of years, depending on the time required for construction. The cost of maintaining the whole system on completion would be approximately £2410. compared with £1495 for the present system. It is suggested that a rate| should be levied for this purpose. When the report was received, the chairman (Mr C. T. Aschman) suggested that a subsidy of £4 for £1 should be asked for, as the district was already heavily rated, and in some cases there was a double river rate. The scheme was necessary, but it could not be carried out only by rating the landowners there. A small subsidy would make it impossible to carry out the work. Therefore the Soil Conservation and Rivers Control Council should be asked for a very generous subsidy, for the scheme would bring into production some of the best land in the counThe chairman of the North Canterbury Catchment Board (Mr W. Machin) said the board hoped to be able to carry out the scheme, which would benefit an enormous area that had been causing trouble for generations. There could be nothing more in accordance with the wishes of the Government than this comprehensive scheme. Diversion Works The area covered by the scheme includes part of the Oxford County, the major parts of the Eyre and Rangiora Counties, and the boroughs of Kaiapoi and Rangiora. Most of the minor portions of the scheme is directly dependent upon the diversion of the Eyre river to the Waimakariri, and the diversion of the Cust river to either the Ashley or Eyre rivers. Without these. Mr Harris said, no complete land drainage scheme of the areas east of the rivers to the coastline could be devi?ed adequately. The schedule of works proposed in the scheme, and the estimated costs of construction, are as follows: (1) Eyre river diversion to Waimakariri river (Oxford County)—£llo.ooo. The length of this diversion from the Eyre river below the WaimakaririAshley Water Supply Board’s siphon to the top of the terrace at the Waimakariri would be seven and a half miles, and there would be a. drop of 60ft to a secondary terrace, followed by a tail race of approximately one mile. The excavation of 1,133,000 cubic yards of the main channel would cost £45.000. One main siphon and six small siphons would cross the channel to take care of existing water races. Flood waters would be collected in an outlet pool and led off by the tail race to the Waimakariri.

(2) Cust river diversion to Eyre river (Oxford County)—£2o.ooo. The intake for this would be situated at the present shingle trap on the Cust river to the north-east of Starvation Hill, where an earthen dam would be constructed with a siphonic spillway embodied in it as a safety factor. The amount of excavation for the three and a half mile channel would be 189,000 cubic yards. Three bridges, one for road and rail purposes, are proposed, and four siphons to deal with w&ter races. This work would deal with Bennetts creek, and form an excellent cut-off to prevent drain and surface waters above Carleton going down country and to the Cust valley. (3) Cust valley drainage works (Rangiora County)—£3lso. With the Cust river diverted and the drain cut off to the Ashley river at the head of the Cust valley, the clearing and cleaning of the Cust river down to Stoke is suggested. The length of the stream is seven and a half miles. Plans for Drainage (4) Drainage south side of Eyre river up to Parish’s ford (Oxford and Eyre Counties), £BBO. Five drains would deal with the balance or all of the under-current after the diversion of the Eyre. (5) Seven new drains to Eyre river, north side (Eyre County)—£49oo. These drains are designed to cut off surface waters and under-current and lead them to the Eyre river, also to cut off the streams north of the North Eyre road in four places and avoid the water going down and adding to the flooding of Mandeville. Ohoka, and Kaiapoi. The drains, together with the Cust cut-off drains, would also give great relief to the troublesome Ohoka stream.

(6) Collier’s creek (Rangiora and Eyre Counties)—£sBs. This involves enlarging and banking three miles of the creek with 62 chains of new drain and culverts at Early road. (7) New cut-off drain (Eyre County)—£37o. This would run for 70 chains along the land and road west of Mr H. E. Evans’s farm at Fernside.

(8) Diversion of Dockey’s creek to Cust river (Rangiora County)—£4Bo. This creek now runs across country and. adds materially to the surface flooding of the former Rangiora swamp. The diversion would be 42 chains long, with two siphons for water races. *

(9) Diversion of two creeks at Fernside to Ashley river (Rangiora County) £1370. These two creeks carry the surface run-off from the downs at Fernside. The smaller one contributes to the flooding of the highway, Rangiora, Flaxton, and Cam areas, and the larger blocks traffic on five roads during floods. (10) Ohapuka drainage. 1200 acres (Eyre County)—£7oo. This involves the diversion of the drain at the outfall to the old north branch of the Waimakariri. cleaning and regrading the construction of new drains, and the cleaning of 75 chains of service drains common to more than one owner.

(11) Line road drain (Rangiora County)—£l3s. This invqlves stoobanking and the provision of a concrete wall and a floodgate. (12) Cut-off drains to Cust river, south side (Eyre County)—£429o. The work here involves the cleaning and clearing of several drains, some excavation work, and the clearing and regrading of the Ohoka Stream. (13) Mclntosh’s drain (5 miles 30 chains)—£l9s. This involves regrading and the provision of a new culvert at Woodend road.

(14) Saltwater creek (4| miles)— £235. Cost of regrading and clearing. (15) Drains in Oxford Countv area east of Ashley Gorge road —£1350. The present drains and creeks have a very sharp grade and are contributing a large proportion of the shingle in the lower reach of the Cust river above the Cust valley. It is proposed to nut in concrete drops to break the grade and clean the drains out. and also construct a cut-nff drain for 140 chains to the Ashley river. Cam River Tributaries

(16) Taranaki rreek (7 miles)— £3500. For clearing, regrading, diverting. and provision of new culverts. Cre“V +o be done up to the west side of Coldstream road. (17) Waikuku ereek and tributary at north road (5 miles)—£lolo. Clearin*, regradin*, and diverting to a noint 40* chain* west o* Smart’s road with orovision for a lower level culvert at Qrnc-cr. n ’ s roa( j (1R) Cam river and tributaries—£lsoo. For clearing and. regrading.

The improvement of the upper reaches of the Cam tributaries is classed as very necessary. They are the Cam or Mill stream, the North brook, which takes all the drainage of the Borough of Rangiora. and the South brook. (19) Ohoka road drain (near Kaiapoi Borough)—£2l4o. This work is an all-in alteration to the present system, which is inadequate to deal with excessive storm waters. The proposal is to by-pass all the waters along the Ohoka road by regrading the present drain from the Island road corner to the Kakanui creek near its outfall to the old south branch of the Waimakariri and diverting the waters that at present cross by culverts across the Ohoka road and run to the old north branch.

Mr Harris emphasised in his report that maintenance of such a project ‘ after it was completed was a vital Is-1 sue, and the efficiency of the best-de- 1 signed drainage scheme would be low- j ered probably 40 per cent, in a short I time if it were not properly maintained. Therefore it was suggested' that a rate should be levied for the purpose. This rate would not be necessary during the construction period other than over minor parts of the scheme that were not dependent on the major diversions.