THE KIWITEA STREAM CHANNEL.

Feilding Star, Volume XVI, Issue 271, 20 May 1895, Page 2

THE KIWITEA STREAM CHANNEL.

TO TIIE EDITOR OF TIIE STAR. Sin,— There are two causes for the destruction caused by the current of streams or rivers. One is through snags or waterlogged trees becoming fixed in the channel, creating a shallow, on which timber, debris, and gravel, collects, forcing the channel against one or both banks. The other cause is (unfortunately in the case of the Kiwitea stream) owing to the strata composing the banks being a mixture of heavy sand, gravel, and large boulders, with light line sand and soluble clay. This formation, being easily undermined by the current, is continually placing obstruction in the channel, by piling up heavy sand and gravel beds on the lee side of the current, and often raising the channel bottom by those means. This deposit having all the light particles carried awa}' or dissolved becomes much more impenetrable to the action of the current than the banks on either side of the stream, and so the current will go ou eatins' its way into the banks unless some artificial means are adopted to minimise the quantity of drift timber and to clear out the channel, so as to induce the current to run away from the banks in which work depth is of more importance than width. This work may seem very great in case of a river running through a sparsely populated district. Not so, however, in regard to the Kiwitea stream, and the work would be the means of preventing great obstruction where a concrete wall to protect the bank would be of no avail, but would in turn become an obstruction from the current forcing its way under, over, or round at the back of it. Keeping the channel clear and deepening it in dangerous parts should be done by private property holders several miles above the site of the proposed new bridge. In some cases it would be necessary for local public bodies to assist them by money or labor, because if this is not done, but only a portion of the stream near the bridge s : te attended to, a great bend of the stream may eventuate from the foregoing causes, which would gradually destroy all that was done in the lower part of the stream. A great deal can be done at no great cent by removing snags at once, and also part of sand and gravel deposits where they terminate in a point extjndiag far into the channel confining the current in a narrow space and foicing its full force against a friable bank on the opposite site of the stream. In my travels I see many of these projecting points, and why they are allowed to remain until mischief is done is a mystery. Large boulders scattered about the strt aoi-bed are an obstruction and should be removed and made use of to protect soft or weak parts along the banks, care being taken to give the main force of the current room, if not they may as well be removed out of the way alfogetheri Above and below the old bridge the stream has commenced to undermine the front, and to force its way in towards the upper side of the high bank near where I understand the site of the proposed new bridge was chosen. By deepening the channel the pressure of tho current against the banks is reduced, and the current obtains a better grip of the channel, and so two objects are gained, and although a succeeding fresh may fill up and entirely alter the channel, yet the stream-bed would be generally lowered in the vicinity of the work. The object should be to divert the current towards midstream, and very little labour will accomplish this if done at once. I cannot say whether it is within the power of the local bodies, or Engineer, to alter the site ; but something should be done towards diverting or clearing the main channel. If any gravel is required to metal or patch up Kimbolton road on either side of stream for some distance, I think it would be worth while to cart the gravel for the purpose from the stream channel, as every little helps, and there seems to be no part suitable for a bridge site in the vicinity until something is done in the foregoing way. I am, etc., F. J. Knox.