A short and wide river, it flows southwest and could be considered an arm of the northern Kaipara Harbour.

The Otamatea is formed by the confluence of the Wairau and Kaiwaka rivers and the North Auckland Line crosses at this point.

Almost 300 metres (330 yd) wide at its origin, the river widens to 1.8 kilometres (1.1 mi) by its mouth opposite Tinopai.

They passed fire-swept wastes, and blackened ranges and valleys, where denuded kauri trees, now often standing alone like giant spectres, held up their bleached heads imploringly to the sky.

Once a gully opened out upon a dark level wall of stiff kahikateas, and once a break in the ranges revealed, on a distant green hill, a solitary house beside a clump of friendly pines.