WAIKOA TIDAL BORE.

New Zealand Herald, Volume LI, Issue 15560, 18 March 1914, Page 8

WAIKOA TIDAL BORE.

NTERESTfNG PHENOMENON.

TWELVE MILES AN HOUB.

RAFTS BROKEN UP.

The presence of a tidal bore in the Northern Wairoa River is not generally known to the bulk of residents on its banks below Dargaville (says ooir Dargaville correspondent), but to those living in the upper reaches of the great waterway, the tide inrush is watched for daily during the summer months. It is seldom noticed at, and south of, Dargaville, but at this period of the year, when the down-flow is comparatively feeble, it is at times observable near the borough, which is situated close on 40 miles from the harbour entrance. As the bore sweeps, past Dargaville it gathers force, and at Tangowahine, nine miles further up-stream, it becomes very noticeable. At the head of the Maunganui Reach it attains its maximum height and force, and at Omana, the river terminus of the North Auckland Main Trunk Line route, 65 miles from the Kaipara Heads, its strength visibly wanes, and disappears before the first of the flood reaches Tangiteroria. In the Maunganui Reach, oarpropelled boats find it necessary to take to mid-river in order to escape being swamped, and stationary log-rafts become quickly dismembered. On many occasions the heavy rafting-chains are snapped, and rafters are always on the qui v:ive for the bore approach at this season of the year. Its speed of travel is assessed at 12 miles an hour, and numerous instances are reported of boatmen having attempted to travel on its crest, only to find themselves sadly left in-the rear in violently rocking crafts. The height of the bore" in midstream appears to be only about 12in, but the wash on the river banks is surprisingly heavy, and as the swell passes, the hsvei of the tideway is raised often as high as 3ft. On a still evening, the approach of the bore ■ can be heard two miles away, its noise rivalling that of a large „ vessel travelling under a full head of steam, and the sight in the Maunganui Reach is, at times, somewhat awe-inspiring. No damage other than to rafts is occasioned by this summer tidal wave, but inexperienced boatmen have had momentary -raisings, especially at abnormal spring tides, when making their first acquaintance with the Wairoa bore. It is interesting to note that the tide flows 80 miles up the Northern Wairoa, and that? high-water at the Kaipara Heads means low-water in the Mangakahia and Wairua tributaries,, and vice versa.