THE PAST
Of all our natural features, rivers may be the most valuable and attractive. Their waters provide for life’s basic needs; they support communities of plants, animals, birds and fish; provide corridors for movement and where these uses coincide, are frequently the location for settlements.
Whilst their water levels may fluctuate, rivers are generally resilient to change. A great example of this can be seen in the Avon River in Christchurch, New Zealand. In February 2011, the city suffered a devastating earthquake. This damaged over half the buildings in the city center and destroyed thousands of residential properties around the banks of the river.
Historically, the Avon River ran through the heart of Christchurch, forming a natural edge to the bustling activity of the city. Whilst the tremors of 2011 brought many of these businesses to the ground, the river continued to flow and its tree-lined banks remained largely unaffected.
As Christchurch started to plan its regeneration, the river was the obvious place to begin the process of renewal. It had strong historic connotations for both the Maori and European communities and now it had the chance to play a pivotal role in its future. One of the fundamental tenets of Christchurch’s regeneration process is ‘a healthy river, a healthy place’.
A simple concept that believes if the river is in good condition, the land and people around it will be similarly healthy.
Historically, the River Avon was the place the Ngai Tahu, the local Maori tribe, went to gather food and plants. The spring fed Õtãkaro/Avon River system had gravel habitats and the clear water and surrounding marshland provided an abundance of wildlife.
Compared with urban watercourses in other world cities, the water quality in the Avon has always been good. However, years of human settlement along its margins have had an effect leading to a decline in its health. Today, the river suffers from the deposition of fine sediment and the lack of habitat diversity. The width of the river, really only a creek when encountered by the first European settlers, has increased over time but the volume of water it contains is now too low, leaving many stretches so shallow that they are unable to support insect and fish life.
The slow speed of flow combined with the shallow gradient of the river also means that fine sediment accumulates on its bed. This sediment then smothers the rocks and gravel, filling the spaces where invertebrates and small fish like to live and breed.
Whilst the water quality is generally good, particularly when compared with other urban rivers, it does decrease during heavy rain when outflow from adjacent streams and drains bring in contaminants. The earthquake and the subsequent large-scale demolitions, together with the current intensive construction works have all added to this problem.
Vegetation has also suffered over recent decades with native noble trees replaced by more competitive plants introduced from all over the temperate world. This has resulted in the loss of natural character, ecological function and landscape linkages. It has also led to the loss of a cultural connection with the natural heritage and there is both a community desire and statutory duty to preserve it.
THE FUTURE
Whilst there is much work to be done, the river remains a wonderful asset for the city and the ambition is to use its leafy corridor as a strong green thread running through its heart. The new river corridor will be made to work hard; re-establishing itself as a natural watercourse, strengthening its role as a linear park, providing an inviting location for walking and cycling, creating new places for activity and providing attractive settings for the numerous commercial and residential buildings to come. Quite a task for a small river but one that is highly achievable.
Beginning with the river, small scale changes to its lower banks will help to narrow its course and speed up flow. This will prevent sedimentation, which will once again provide places for fish to live and breed. Through the heart of the city, lawns and mature trees of mainly European origin bound its course. These create a unique character that is cherished by the local community.
There is however the opportunity to make the river corridor even richer and to create a real ‘botanical adventure’, an approach which combines native and exotic plants to establish a riverside ecology unique to Christchurch.
The greater use of native plants, i.e. those that would naturally occur within this location, will help attract insect and bird life back to the city center.
Many of these plants also have strong cultural significance for the Ngai Tahu and will help to strengthen the concept of Mahinga Kai; this is one of their key values and refers to traditional food and other natural resources and the places where they are obtained. The land now occupied by the central city had always been a traditional food gathering place for Ngai Tahu, with its water and rich soil providing an abundance of birds and fish.
In ecological terms, the edges of the river also have an important role to play. Marginal planting, waterside species with their roots in the water, together with grasses and herbaceous planting higher up its banks will all help to create a more diverse community. In turn these will support wildlife and together the whole environment will become more ecologically diverse.
The new approach will be about giving nature a helping hand but it will also be about people and how they are able to use the landscape. Cycle paths and footways, including a pedestrian- focused promenade running the length of the river, will encourage more activity and provide inviting and safe routes. Along these, residents and visitors will be able to walk to all the destinations of the central city. Along the way there will be places to meet friends, exercise or just relax and enjoy the surroundings.
A variety of new spaces will also be established, some green and simple providing easy access to the river’s edge, others more civil, creating settings to historic structures or places for gathering and performances. These locations will be able to support a multitude of activities with the goal to have the river corridor teeming with life and vitality.
In moving forward with this process of renewal there is much to be positive about. The health of the river and that of the wider community can be improved through a variety of measures, be it by increasing the diversity of planting along its edges, linking habitats to ensure fish, insects and birds can move from one stepping stone to the next or treating storm water before it enters the river.
Whilst Mayflies are now extinct and freshwater Crayfish and Mussels have all but disappeared, it’s possible that they can be encouraged to return. More positively, fish diversity remains good and there is every chance that Bluegill Bullies and Longfin Eels will once again become common.
The real indicator of success will be when Inaka, the local Whitebait, are once again attracted to this stretch of the river and can be regularly seen by the community of the city.
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The Avon Precinct is but one section along the length of the river and the ultimate goal is to create a ‘Springs to Sea’ experience which connects the headwaters of the river to the ocean. This will be a complex goal but one that will help to marry ecology and the natural landscape with Maori and colonial characteristics.
Special thanks to Shelley McMurtrie EOS Ecology www.eosecology.co.nz
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