LAKE FORSYTH DRAINAGE SCHEME.

Press, Volume LIII, Issue 9344, 19 February 1896, Page 5

LAKE FORSYTH DRAINAGE SCHEME.

[COM-fU-UTliD.]

The statutory announcements of the Akaroa County Couucil iv reference to the raising of & loan of £2000 under the Loaus Acts, to be applied to the'purpose of con. structiug pei'inaucut drainage works at the foot of Luke Forsyth, involves isa ies of so important a nature as should readily recommend themselves to the support of the County ratepayers. A short general description of tne proposed scheme may serve to make the project of the County Couucil better appreciated

The watershed of the Little River Bide of the Peninsula embraces in its area the Western Valiey aud the Xerawera and Okute Valleys, discharging the full force of their drainage into Luke Foray Ui at its north-eastern extremity. This accumulation is further supplemented by the numerous water-courses and the surface drainage rapidly descending from the steep ranges towering over the north-western and southeastern boundaries of tbe lake. The formation of the Lake is due to the closing in of an arm of the sea by the banking up of the well-known shingle drift across its mouth, thus creating a reservoir from which there is no escape for its waters save by the slow process of evaporation or filtration through the shingle-bank to seaward. Consequently the periodic floods rapidly overflow aud submerge the low-iyiug cultivated lands at the head of the late, aud the four miles of main road skirling its north-western margin. With tlie exception of the railway line the main road forms the only through channel of communication with Akaroa sand the plains on the south side of the Peninsula. The ultimate safety of the road is in effect the ration d' €tve for the carrying out of the Council's scheme. Under the existing state of things, when floods occur the lake ia let out by cutting a channel through the shingle beach already mentioned, until an outflow is obtained, when, by the increasing Bcour, a gap five to six chains wide soon clears itself, and the lake is rapidly reduced to a low level. To attain this result, however, the water must be allowed to rise to suoh a height as will ensure sufficient pressure to produce the condition of things stated, and that, moreover, when the vexation, damage and danger of the flood has asserted itself.

Space will not permit of discussing here the merits of the many schemes that, have from time to time been promulgated for retaining Lake Forsyth at a low level; but expert investigation proves, aud there is a general opinion among those who have a knowledge of suoh things, tbat a properly arranged system of oulverts of sufficient sectional area and strength would effectually meet the case.

It is proposed to construct four large culverts through the shingle beaoh, consisting of 240 ft of conorete aroh, with strong walls and invert on the intake or lake side, and continued thence by a length of 220 ft of timber boxing on the seaward side to the outfall, making a total length of 460 ft for each culvert. There will be a lead of about two chains of open channel pitched with heavy stone to form an entrance to the culverts, whioh will be further protected at the opening by substantial wing walls. The strongly agglutiuated nature of the shingle bank renders it well capable of carrying concrete, and where on tbe seaward side the strata is friable the wooden portion of the culvert will be secured with stout piling. The intakes will be so arranged as to tap the lake at its lowest level, and it is estimated thereby to secure the reclamation of some hundred- of acres. The conorete oulverts will have a width of 6ft in the clear, 3ft height of walls, with an additional 3ft to the crown of the aroh. The timber portion will be 6ft by 6ft in the clear, substantially framed and fastened, and entirely constructed of Tasmanian hard woods.

Tenders will be called, and the work proceeded with as soon as the necessary formalities for obtaining the loan are assured.