Some years ago, events were evolving around the formation of plans to dredge the estuary, to deepen it and turn the waterway into a major Canterbury attraction.
The Estuary is a geologically young coastal feature, as around 1500 years ago a ready supply of offshore sand from the continental shelf, and the longshore drift of sediments from the Waimakariri and Ashley Rivers built up its edge. The spit continued to develop from alluvial wash moved southward from the mighty Waimakariri River, closing off what was a small bay and forming Te Ihutai, the Avon-Heathcote Estuary.
As Christchurch grew, unmanaged development continued along both urban rivers and combined with the dumping of waste beside the estuary, led to serious environmental decline, eroding the ecological and cultural health of the estuary and its catchment.
Early settlers who found out the swamp surrounds were not necessarily good for English constitutions, set about draining parts of it, and dumping industrial waste into the rivers leading off it.
In 1956, a century after Christchurch was founded, the Drainage Board built the Bromley oxidation ponds for a new sewerage scheme that discharged treated wastewater directly into the estuary. Although the sewerage upgrade brought health benefits to residents, the continued use of the estuary as a bucket for the city’s waste, perpetuated the history of disregard for mana whenua (indigenous users of the area).
The upgrade of Christchurch City’s sewerage system came with the promise of improved water quality. A commitment honoured in March 2010 when the wastewater from the Bromley Sewage Treatment Plant began discharging three kilometres out into Pegasus Bay via an ocean outfall pipe.
However geomorphic processes intervened and the Canterbury Earthquake Sequence between 2010-2012 caused significant uplift of areas of the estuary, disrupting the ecological system of the mudflats, damaging sewerage systems, and once again the unmentionables flowed back.
This at least has brought a re-think about ecology and how incredibly important Te Ihutai actually is, not only for its previous Mana Whenua guardians, but for all of us, and future visitors and tourists following the Avon river corridor from the city to New Brighton.
Going back to 70 or so years earlier, this new direction could have been a lot different had the Canterbury
Progress League got its plans past the Drainage Board and other authorities. The League was an
organisation with the role of publicising Canterbury as a destination for tourists and new immigrants.
Its proposal for the estuary (see below) and based around an increase in depth to create an aquatic
park/playground. An artificial nature sanctuary island to be built as one side of a six lane international rowing
course, along with mooring and swimming facilities around the inlet.
The fact this venture never proceeded meant a large flock of exhausted and starving Godwits very thankful the 12,000km journey from the Arctic, would not end in finding their feeding grounds under at least 1.5 metres of water.
Sometimes it is a thin line between direction and deliverance, and Te Ihutai is fighting back, but imagine
trekking over the Bridle Path in 1850 (see sketch) from the first four ships, looking down on the landscape
and saying: “Yeah, nah, not suitable for a city, lets try further along the coast”.