RIVER PROBLEM.

Patea Mail, 13 November 1880, Page 2

RIVER PROBLEM.

The dredge for Wanganui harbor has arrived in sections, and is being put together at Bett’s wharf. This dredge is to work out an interesting problem. The Harbor Board bediove or have a hopeful expectation that the extensive mud flats which impede navigation just inside the Wanganui bar can be dredged away by the slow operation of one small machine. The experiment is worth trying, but is very doubtful for the reason that the silt accumulation is continuous, and the daily deposit of up-river sediment may fill a small artifical vacuum as fast as the dredge scours it out. The breadth of the stream is the

real difficulty ; for while these silt de- J posits could be swept away only by a volume of water greater than that which now shows itself to be ineffectual for the purpose, the broad extent of these deposits is the real impediment to their removal by scour artificially induced. If the present volume of water could be made to scour through a narrow channel, say one-third the present breadth, that scour would effectively deepen the channel within that narrow space. It is conceivable that the month could be divided by training walls into a narrow channel for navigation and a broad channel for tidal overflow ; and if the walls so placed could be maintained, a deep navigable channel would be a certainty. The problem is this: Can a deep channel be dredged through the mud flats, and being made can it be maintained by the ordinary outward scour?