Dr Catherine Knight
Christchurch: a city haunted by its environmental past?
February 26, 2011
It is with both horror and immeasurable sadness that I contemplate the tragic consequences of last Tuesday’s massive earthquake on the city that I lived in for 8 years, and which I still regard with immense affection. I cannot even begin to imagine how life must be like for its residents today, especially those who have friends or family who have perished.
No one could ever have contemplated this level of devastation to a city that was so established – historically, and seemingly, structurally. But some clues to what has led to this unprecedented scale of destruction may be found in its environmental past.
Christchurch was one of New Zealand’s first cities: the first pioneering settlers made their home there in the 1840s, but it was in the 1850s that organised settlement began, with the “first four ships” from England arriving at Lyttelton Harbour. The founding fathers of Christchurch showed great foresight, laying out the city in a grid pattern, with numerous parks, squares, and tree-lined avenues and waterways. No expense or labour was spared in the construction of the city’s iconic buildings either: many of these are the most beautiful examples of stone masonry in New Zealand, and make the city the special place that it is.
But much of that – literally – came crumbling down on the 22nd February 2011, in what was technically “only” an aftershock of the September 2010 quake.
This time, the epicentre was in Lyttelton Harbour – much closer to the city than the September quake. But it seems that much of the damage has been concentrated either in the inner city or along the city’s many waterways. The root of much of this damage is liquefaction, a phenomenon whereby soil loses its strength and cohesiveness and takes on the constitution of liquid, usually in response to a major earthquake.* A key factor which determines the extent of liquefaction is the depth of the water table.
So, why would Christchurch be more prone to this than other cities? Originally, the area that is now Christchurch was an extensive coastal wetland, thickly forested with matai and totara, and other swamp forest species. However, much of this forest was burnt off (whether deliberately or accidentally, we do not know) by the earliest inhabitants of the area, the so-called Moa-hunters (or Archaic Phase Eastern Polynesians), who arrived in the area possibly around 1000 AD.
By the time Europeans arrived in the 19th century, there were only isolated patches of forest, with a mixture of tussock grassland and swamp making up most of the area. One of the earliest descriptions of what was to become Christchurch is that of Captain W.B. Rhodes, whose barque Australian visited Port Cooper in September 1836. He climbed the nearest saddle of the Port Hills and saw a vast grassy plan with two small patches of forest (Riccarton and Papanui), and observed “All the land that I saw was swamp and mostly covered with water.”
For that reason, as Geoffrey Rice points out in “Christchurch Changing”, the earliest European settlements were on Banks Peninsula, rather than down on the flats. But eventually, over the course of the subsequent decades, the settlers succeeded in draining the wetlands for farmland and settlements, and channeling the many waterways into two more “orderly” rivers: the newly named “Avon” and “Heathcote” (known as “Otakaro” and “Opawaho” to the Maori of the area). Their efforts to establish a vibrant, thriving and attractive city were apparently successful, with Christchurch becoming the second largest city in New Zealand, and its growth showing no signs of abating.
And so it appeared that successive generations’ efforts to subdue and control the natural environment that formed the foundations of Christchurch City was complete. But after a century and a half of more or less being kept under control, that nature has shown itself – combined with formidable seismic forces – to be far from subdued. Perhaps our sense of confidence and self-assurance in our own powers over nature are less justified than we thought – with consequences that are more tragic than anyone could have possibly imagined. I hope there will be lessons here for all who will be part of creating a vision for our cities of the future – cities that are not only functional and attractive, but also enduring and safe for those who live in them.
*Incidently, I also lived in Osaka, Japan, when the Great Hanshin Earthquake hit the port city of Kobe in 1995, killing 6,434 people. In this earthquake, one of the areas that sustained the most damage was Rokko Island, an artificial island created literally by scooping earth from nearby hills and dumping it into the sea. This island also experienced intense liquefaction as the soil from which it was constructed loosened up and moved, destroying buildings and infrastructure.
Photo top left and top right: The Provincial Council Buildings, on Durham Street (with the Avon River in the foreground) and the Christchurch Cathedral in their former splendor. The Provincial Buildings were built between 1858 and 1865, and were designed by Benjamin Mountfort, Canterbury’s leading Gothic Revival architect. Above left: The Provincial Buildings today. It is unclear whether they – or any other of the city’s historic buildings damaged in the quake – will be able to be rebuilt. Bottom right: Christchurch, in May 1860. Looks south-east from the Provincial Buildings, towards Oxford Terrace and Gloucester Street. Avon River can be seen in the foreground. The deforested Port Hills can be seen in the background. Taken by Alfred Charles Barker. Not to be reproduced without permission from Alexander Turnbull Library ref. ID 1/2-022722-F.