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Ngā Tohuwhenua Mai Te Rangi: A New Zealand Archeology in Aerial Photographs
Drains and trenches
Drains and trenches
Mainly in Northland, but also as far south as Kawerau in the Bay of Plenty, drains or trenches are a feature of gardening areas. The functions of these are also controversial. Were they indeed drains, pure and simple, or trenches which served to mark boundaries where stone or scrub was not available? 22 Did the trenches offer unique gardening conditions, planted in their own right, for example, with taro planted at the bottom? A drainage function may seem obvious, but it was probably only one of several functions. In Northland drains or trenches occur in open swamps, at the foot of hill slopes and in small basins in volcanic stonefields. In the far North near the Awanui River, they lie in two broad patterns: one is a deliberately artificial, more or less rectangular pattern of some intricacy, delineating plot boundaries as well as serving to drain. The other is the simple modification of natural drainage features such as rivulets or erosion runnels. 23
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Drainage pattern for gardening on the alluvial flats of the inner Rangaunu Harbour, near Kaitaia
The lines that show in the soil at this time (August 1944) were originally trenches or drains constructed by Maori, probably in the seventeenth or eighteenth century. They appear to follow and enhance a natural drainage pattern, showing clearly where natural streams enter the sinuous inner reaches of the estuary. The ditches were probably used for taro while the beds between were for kūmara. The ditches would have filled with dark, organic-rich mud over time, which would be periodically thrown on the gardens. When the ground was ploughed deeply, perhaps for the first time in the 1940s, the pattern of the channels has shown against the lighter coloured subsoil. Modern European drains have been cut over the older drains, and form a different and more sharply defined pattern. The river is about 16 m wide, and the typical trenches are 1 to 2 m wide.
The area shown is on the lower tidal reaches of the Waipapakauri and Waimanoni Creeks, about 2 km west of the Awanui River; mangrove trees show on the edges of the river. The airfield was a wartime measure and no longer exists.
At least two pā defended by double ditches and banks may be seen. One is at top left; the other is at the eastern end of the light-coloured debris from the creation of the prominent west to east drain. Other possible pā lie on each side of the river just to the south of the prominent drain.
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Trenches on a slope near Marsden Cross, Bay of Islands
A particularly fine example of a complex of trenches. The lines of the trenches run about 25 m up the slope; the trenches are about 1 m across and lie at 5 m spacing across the slope. The trenches may be a type of crude irrigation, i.e., irrigation without elaborate water reticulation to the garden plot. Intercepting groundwater towards the foot of the slope, they may form artificial springs which would assist the growth of taro in summer and late summer dry spells. The taro would be planted actually in the trench, hence the close spacing. This particular example has a perimeter ditch running around the top of the trenches showing clearly at right.