The city of Christchurch, New Zealand is located on the eastern side of the South Island and has a population of around 340,000 (2006). It is not widely known that New Zealand was the last significant temperate land mass to be peopled, the first Polynesian migrants arriving from Hawaiki (Probably in the region of Tahiti) about 700 years ago. This has only recently been confirmed by carbon dating of rat bones and rat-gnawed seeds, since prior to human activity the only mammals in the land were two species of bat.
There was sporadic activity by Europeans involved in whaling and sealing from the last years of the 17th. century but large-scale settlement by Europeans did not begin until after the Treaty of Waitangi in 1840 signed between the British Crown and many (but not all) of the tribes and clans of the indigenous Maori people.
Christchurch the largest city in the South Island, in the province of Canterbury, experienced the first significant wave of European migration in 1850 with the arrival of "the first four ships" carrying settlers from England. It is said that it was an ambition of these settlers to create a "new and better England" and they set about the task with great vigour.
The site of Christchurch is close to the port of Lyttelton but separated by a significant barrier, the "Port Hills", over which the settlers trudged and from which they could look down on their future home and the Canterbury Plains spread out beyond. Unfortunately much of the land designated for Christchurch by the organizers of this first migration was swampy and one of the early tasks was to drain these and begin farming productively.
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As with any city the stormwater system was built around the natural drainage the core of which for Christchurch were the three small spring-fed waterways Heathcote, Avon and Styx.
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The spring water providing the base flow in the urban rivers originates from the Waimakariri River just north of Christchurch (Figure 3) and by the time the water enters these waterways it has been filtered through kilometers of gravel and is sparkling clean, creating a special character much loved by the citizens. In their original purely spring-fed state these rivers would rarely have flooded and still seldom create trouble, but the creation of a modern urban storm-water system designed to remove water as quickly and efficiently as possible has made things worse both from the point of view of flooding but also of water quality, both impacting the river ecosystems. Nevertheless the rivers are nearly always attractive to locals and tourist with the Avon, which flows through the heart of the city, having iconic status.
With them, the early settlers brought the things most loved from England in order to make a living and recreate their homeland as nearly as possible. This meant animals and plants together with technology to transform the landscape. They also brought attitudes which tended to ignore, undervalue and brush aside things indigenous to the land, including the Maori people. Over the next 150 years the cityscape developed and evolved a particular character which led to the comment that it was "more English than most English cities". A consequence of this was that the indigenous flora and fauna faded into the background against the dominant "English" landscape and while this attracted much favourable comment there was a growing sense of imbalance and loss, especially of the wetlands.
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CHRISTCHURCH URBAN AREA AND RIVERS
At the same time the developing city and stormwater flows were creating flood problems in the lower catchments, especially the Heathcote, which required significant engineering works. A major re-think in the early 1990s led to a new river, wetland and drainage management philosophy (Watts and Greenaway, 1999) which encourages managers and designers to work with natural features and processes in the landscape. …