Farmers of the Cashmere and Hoon Hay Valleys from 1850 – 1890 converted these wetlands to farmland by digging straight drains that eventually re-routed the Cashmere Stream. Now, in an attempt at turning back time, part of the original riverbed of the Cashmere Stream is being unearthed and the stream is being restored to its original path.

In 1850, the Cashmere Stream was quite short, sourcing its flow from a large, spring-fed wetland in the area between Sutherlands Road and Sparks Road. The wetland was vegetated by flax, raupo and toetoe with a scattering of kahikatea and totara trees. At this time, the Cashmere Stream was a relatively short stream running beside what is now Cashmere Road before it joined the Ōpāwaho Heathcote River.

Draining the swamps The Cashmere Valley wetlands as they were in the 1880s would now be viewed as an essential and valuable sponge to hold back floodwaters, filter runoff and store carbon.  To the settlers of the 1800s, however, the wetlands were undeveloped rich soils just waiting to provide bountiful harvests and excellent pasture to farmers willing to tame the water.  Farmers such as John Cracroft Wilson employed gangs of labourers, some from India, to dig drains across the valley, divert the stream into drains, fill in the original stream bed, clear the native vegetation and sow grass seed to create pastureland.  Fortunately, if you tried to do that today, the Resource Management Act and its National Policy Statement for Freshwater Management would foil you at the first step.  In the 1800s, such actions got you into parliament, with a knighthood.

Recreating wetlands The Christchurch City Council (CCC) is now working to recreate some of the original wetlands to assist with the retention and slow release of stormwater to prevent flooding in the lower reaches of the Ōpāwaho Heathcote River. While these recreated wetlands will not be exactly the same as those of the 1800s, they will eventually function in much the same way as the original. The wetlands will improve the water quality, increase carbon capture and improve the habitat for native freshwater fauna.  As part of this mammoth task, and in conjunction with the Cashmere Stream Care Group, the Cashmere Stream itself is being enhanced along its length by reshaping the banks, introducing interruptive elements such as logs and rocks to create habitat, putting some meander into otherwise straight runs and revegetating the banks with native trees, shrubs and grasses.  

Turning back time As part of that enhancement exercise, largely funded by the Ministry for the Environment, the CCC is about to start exhuming a section of the old Cashmere Stream bed.  Despite the fact that it was filled in more than a century ago, and farmed over ever since, it is possible to approximate the likely track of the original stream bed.  Once the channel is re-formed, its banks suitably sculptured and the bed fitted with appropriate obstacles like rocks and old logs, the Cashmere Stream will be diverted from the current straight “drain” and will flow in its original path.  That really is like turning back time. You can view full plans of Stage 3 and Stage 4 of this enhancement programme.

Issues with re-creating the original stream bed It sounds easy; just dig out the old bed to its likely gravel base and you are done!  Not so.  For a start, after more than a century of draining and farming, the level of the land has changed and therefore it may be necessary to dig a little deeper than the original.  This in turn raise two issues: the quality of the soils and the vexed question of springs. The passage of the stream through its re-formed channel may unearth and disturb areas of sands that could travel with the water, weakening and collapsing the banks and carrying sediment down the river.  This has to be avoided if at all possible.  Similarly, in excavating the old channel, springs may be encountered: not a problem as far as the water is concerned – most of the water flowing in the Cashmere Stream originates from springs in this area.  The problem arises from the fact that the aquifer that would be the source of an exposed spring is already fully allocated and therefore, from a resource planning aspect, exposing the spring would mean a technical non-compliance “take” from the aquifer.  It is not clear how this will be handled by Environment Canterbury, but it is hoped that good sense will prevail.

Even issues with filling in the current drain  Once the stream is flowing sweetly in its old channel, it is just a matter of letting the old drain dry out and then filling it in: if only!  Perhaps the greatest issue could be with springs again.  When the stream is diverted into its new channel, it is very possible that that will expose the fact that one or more springs have been feeding into the stream in its previous “drain” location.  It will be necessary to seal these springs – and sealing a good-sized spring in an old wetland is no easy matter!  

You can help It promises to be a project well worth watching and being involved in.  The Cashmere Stream Care Group will be calling for community help with planting 12,000 native plants in this area come the autumn – April, May.  We will be publicising it.  In the meantime, you can access much of this area (Stages 1 & 2) on walking tracks that have been laid down throughout the area: you can park in the Hoon Hay carpark off Cashmere Road.  You can keep up-to-date with progress on the enhancement here.